Convert license tags to SPDX identifiers

This commit also converts our own copyright headers to directly use
SPDX, but leaves all other copyright header intact, only adding the
SPDX ident. As far as possible this commit also merges multiple
Data61 copyright statements/headers into one for consistency.

Document internal machine/interrupt.h interface

Every platform has to implement a standard set of interrupt interfaces
that the kernel uses to interract with a machine's interrupt controller.
Providing a single header file for each of these functions provides a
single location to document their behavior.

arm: remove plat/machine/timer.h

plat/machine/timer.h is unused on arm, so remove it and fix up the
includes.

arm: move handleOverflowIRQ to benchmark.h

Consolidate to reduce include complexity and make benchmarking features
easier to find/comprehend.

imx31: use declare_default_headers

- remove unused header files replaced by declare_default_headers
- move interrupt.h -> drivers/irq/imx31.h
- move hardware.bf -> drivers/timer/imx31-epit.bf
- move timer.h -> drivers/timer/imx31-epit.h
- move definitions from hardware.h to plat/imx31/machine/hardware.c

style: set min-conditional-indent to 0

Given we use braces all the time conditional indents do not make code
cleaner.

style: consistently attach return type

Add attach-return-type to astyle

timer-refactor: Move kernel timers and rename

This change moves all arm platform timers to drivers/timer
and renames them to the compatibility string specified in the dts.
Now the correct timer is included at build time based on the dts,
this follows the same pattern as the serial-refactor.
Have moved the arm generic_timer and priv_timer into the timer
folder and updated cmake configs appropriately.

arm: Rename plat_cleanInvalidateCache

Rename plat_cleanInvalidateCache to plat_cleanInvalidateL2Cache to
indicate that it is a L2 cache maintenance operation only.

ARM platforms: use auto-generated kernel_devices

Note that the auto-generated kernel_devices will differ slightly from
the ones present in the kernel until now. When devices have
registers that aren't page-aligned we now always set the appropriate
PPTR to be the start address of the device, while previously the PPTR
was sometimes page-aligned.

Specifically, this change to PPTRs affects:
- bcm2837 intc
- bcm2837 uart
- allwinnerA20 timer

Inline resetTimer for all platforms

- for arm generic timer platforms, we remove resetTimer ->
resetGenericTimer indirection and simply include generic_timer.h
- this reduces boiler plate for platforms that share timer drivers, as
they simply include the one header
- there is far more timer code in the RT kernel, which motivates this
change

Make TIMER_CLOCK_HZ available in timer.h for ARM

The RT kernel needs this value accessible to common functions.

Refactor arm timer ticks calculations

- remove a lot of redundancy
- define TIMER_CLOCK_HZ for each platform (rather than inconsistenly
named variables with inconsist units)
- use the common calculation of TIMER_RELOAD

Refactor memory mapped arm timers

- make them consistent: struct, type and global vars
- typedef the struct definition as volatile
- separate struct, typedef and variable definition
- always cast the pointer as the timer type

Share linker.h between architectures

kzm: fix timer reload overflow calculations

ARM/IRQ: add a function to initialise local IRQ controller for CPUs

Similar to initIRQController(), cpu_initLocalIRQController() has to
be implemented for each platform. For those that are gonna support
SMP, it should be implemented proprely (if required), otherwise
it can be stubbed for single core implementations.

Remove many DONT_TRANSLATE markers.

The vast majority of the DONT_TRANSLATE markers in the kernel are used
to hide __asm__ statements and builtin functions
(e.g. __builtin_unreachable ()) from the C-to-Isabelle parser.

The parser now supports underscore identifiers and many __asm__ statements,
and the builtin functions are prototyped, meaning the vast majority of the
DONT_TRANSLATE markers can be dropped. The remaining markers cover functions
that must be treated specially.

[STYLE_FIX]

Fix arm builds broken in 44ed6adb6

Store active irq in global variable on kzm

The first time the irq number is read from the controller, the interrupt
is acknowledged. Subsequent reads of the irq number result in an invalid
irq number being read.

This modifies the kzm interrupt controller driver to save the current irq
number when it's first read from the interrupt controller, preventing the
need for future reads from the controller until the next interrupt arrives.

SELFOUR-607: inline remaining irq path functions

SELFOUR-519: remove map_kernel_devices duplication

* move devices to static array in hardware.h
* use one higher level function to map them in.

SELFOUR-519: remove more duplication in hardware.c

* move p_reg functions up a level
* move p_reg definitions to hardware.h

SELFOUR-448 Benchmark: Add PMU IRQ support to ARM platforms

Currently supported boards are:
- imx6 (sabre)
- tk1 (Jeston)
- kzm

Refactor duplicated code in hardware.h

One copy to rule them all.

Trivial: move printfs in handleReservedIRQ up.

This wraps the printfs in CONFIG_IRQ_REPORTING
and reduces redundancy.

SELFOUR-402: remove isReservedIRQ

While provided by each hardware platform this function is never called.

Further separate 'release' and 'verification' builds

Originally building the kernel was largely considered to be done in
one of two ways
1. Release build with no assertions, no debug symbols and no printing.
This was generally considered to be a 'verified' build
2. Debug build with assertions, debug symbols and printing

Since then various options were added, such as the 'code injection'
option, which we wanted on builds that did not have assertions or
other options that affected performance. As such it did not depend
upon a debug build and had large warning signs saying that enabling
this in a release build would not give you a verified or trusted
kernel.

Most recently the ability to print from the kernel in release mode
was added. For the same reason that tying the ability to print with
the performance reduction of various debugging was not always desireable.

This change attempts to unify the current state and have a single top
level option to enable a 'verification friendly' build. All other
options (assertions, printing, code injection) then depend upon
this configuration not being set.

Change additional int->word_t due to interraction with the C parser to ease verification

xIntroduce RELEASE_PRINTF, which allows a renamed printf (release_printf) to be used in a release build of the kernel - userful for debugging tests that only fail on a release build of the kernel

ARM: Set the XN bit on kernel mappings that do not need to be executable.

This covers the kernel stack, globals frame and device memory. We shouldn't be
executing in any of these pages, so functionality should be unaffected. This is
primarily a debugging aid.

XN: fix order of vm_attributes in init code and update apq8064

further support for XN bit on ARM

Release snapshot