trivial: fastpath: add config for declaration

c_handle_fastpath should only be declared for fastpath config.
And also fix the style and docs.
This change will not affect the result of compilation.

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.

fastpath: reorganize the code layout on ARM

fastpath_call and fastpath_reply_recv got inlined into a single
function. This could cause loading unused code in cache and
additional jump instructions required in c_handle_syscall.

mcs: scheduling context donation over ipc

After this commit, threads blocked on an endpoint can recieve a
scheduling context from the thread that wakes the blocked thread.

Consistent naming of FaultIP and NextIP in kernel

Always refer to the virtual register that stores the address of a fault
as FaultIP and the register that stores the return for a fault NextIP.

Remove symlinked libsel4 files from include dir

These files can be included normally using libsel4 include paths. This
removes situations where the same file is available under different
include paths due to symlinking into different directory structures.

aarch32: remove obselete code in traps.S

The stack is loaded on the preceding lines of code from
TPIDRPRW, regardless of SMP being enabled or not. Loading ksCurThread
into r7 is from the previous approach of loading the kernel stack and is
not longer used.

SMP: Introduce ENABLE_SMP_SUPPORT

- Make it more readable and less confusing compared to the 'CONFIG_MAX_NUM_NODES > 1' check

Use CONFIG_ variables instead of configuration definitions

Fix: Allow util.h to be included in assembly files

ARM/SMP: Prepare for ARM SMP adding stubs

Currently building ARM/SMP is broken. This commit:
1- Makes it possible to build ARM/SMP with stubs. Run-time SMP for ARM
DOES NOT WORK.
2- Can be a reference for future SMP targets to follow in order to
layout/add the minimal required files and functions needed to support SMP.
3- Builds for Sabre only. In order to support other platforms, ipi
interrupt ID should be defined in machine.h

ARM: Refactor how we get/set seL4 kernel stack

This commit makes seL4 hold the stack address on TPIDRPRW register (PL1 only
Thread ID Register, VMSA, see B4.1.150 section of ARMv7-A and ARMv7-R
edition reference manual).

Originally, the kernel stack was (re-)mapped to a fixed kernel virtual address and
on traps sp is loaded with this virtual address. Reason is to shave up some
cycles/instructions on (fast) traps path instead of having two instructions
(loading global variable pointer and then memory-load stack address from
it).

With ARM pipelining getting smart/complex (from ARMv7 onwards), there is
no noticeable difference in performance between the two implementations.
Furthermore, this change makes it easy for SMP to load different stacks
for each core and do CPU ID arithmetic efficiently. It also avoids the
issues involving (re-)mapping stacks for different cores if we
followed the original design.

Note: the main side-effect to this change is that the kernel stack for
ARM is no longer mapped with execute-never attribute.

SELFOUR-615: arm entry point stubs

SELFOUR-617: one source of memory object sizes

Adds the following constants to libsel4
and uses them in the kernel.

seL4_SectionSize (arm)
seL4_SuperSectionSize (arm)
seL4_HugePageSize (x86 - pae)
seL4_LargePageSize (arm)
seL4_DataFault
seL4_InstructionFault

trivial: fix typo

arm: Remove unused arm_swi_undefined_syscall

SELFOUR-526: ARM - Implement slowpath and restore_user_context in C

SELFOUR-526: ARM - Unify C entry point for system calls

arm-hyp: Push ARM_HYP config check into traps.S

Rearranging sources for aarch32 to 32/*