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.

arm,SMP: Refactor irq_t structure for smp

Explicitly create a struct definition for irq_t on SMP Arm
configurations. This makes it a lot harder to mistakenly use the wrong
irq encoding when moving an irq between a cnode index and hardware irq
number / core. A couple areas where this was being handled incorrectly
was fixed as part of the refactor. When performing an ipi for masking
PPI interrupts, the idx encoding is used as it fits into a single word.

[SMP] Abstracted IRQ indexing to handle PPIs

irq_t is now a "virtual" interrupt type that encapsulates the
information of the core in case of a private interrupt. There is a
couple of macros that need to be defined on the interrupt controller
level to translate between virtual and hardware IRQs.

IRQControl_GetTriggerCore: check for valid target

Add a check to return a proper error when the target node is higher than
CONFIG_MAX_NUM_NODES.

Added IRQ routing to specific core for ARM

Add a new syscall, `seL4_IRQControl_GetTriggerCore`, to get a IRQHandler
with specific target core(s) and trigger method. Only available in SMP
mode.

style: consistently attach return type

Add attach-return-type to astyle

SELFOUR-1491: error if set trigger not supported

So far this is only implemented for the GIC, which most of our platforms
use. Error if this invocation is made on another platform, and guard
calls to the trigger function if it is not supported.

SELFOUR-1491: Modified Arch_invokeIRQControl

It will now return the value coming from invokeIRQControl directly.

SELFOUR-1491: verification updates

- renamed an architecture label so that it begins with ARM.
- changed setIRQTrigger so that it takes a boolean value instead of an int.
- Arch_decodeIRQControlInvocation converts the second argument (trigger)
to a boolean immediately.

SELFOUR-1491: add seL4_IRQCOntrol_GetTrigger

Add a new invocation which allows an irq handler capability to be
obtained with a specific trigger method (edge or level). Obtaining
this capability modifies the GIC state.

archirq: rename missed label to invLabel

Remove redundant IRQInterruptControl invocation, and replace with a mechanism to actually decode arch specific IRQ invocations

Part of SELFOUR-281

SELFOUR-114: remove duplication of seL4_MessageInfo_t, adjust naming to avoid cparser mangling

unsigned int -> word_t

Release snapshot