replacing all ifndef with pargma once

All the kernel header files now use pargma once rather than the ifndef,
as the pre-processed C files do not change while header files
are protected with pargma once. This will also solve any naming issues
caused by ifndef.

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.

Revert "Cache FPU enable state on all platforms"

This reverts commit 186180cf309b365b45c162f7a1f5931f0fc05d7c.

Cache FPU enable state on all platforms

This change broadens the caching of the FPU enable/disable bit from arm
to all platforms to ensure that on x86 time is not wasted on the
fastpath disabling or enabling an already disabled/enabled FPU.

Revert the recent changes to Faster FPU switch

These changes need to be reverted until we can properly test the changes
with all of our hardware online (currently we cannot test on x86
hardware).

This reverts commit a0aeec3b304d16909619bc847197df221c73a0c4.
This reverts commit af0fdc82c23f1e7e3f1e568f6987f5afd0d2150a.
This reverts commit a190a14ecaae688a6b40dd0a699b8f49c2c0631e.

Cache FPU enable state on all platforms

This change broadens the caching of the FPU enable/disable bit from arm
to all platforms to ensure that on x86 time is not wasted on the
fastpath disabling or enabling an already disabled/enabled FPU.

style: correct parenthesis padding

Use astyle's unpad-paren to unpad all parentheses that are not included
by pad-header, pad-oper, and pad-comma.

armv8: Modify enableFpu/disableFpu to support EL2

armv8: Add function isFpuEnabled

armv8: Add disableFpuEL0

This function disables FPU access for EL0 only.

armv8: Add enableFpuEL01

The function enables FPU access for both EL0 and EL1.

armv8/hyp: Add EL2 FPU functions

enableTrapFpu: enable trapping any FPU related instructions to EL2.
disableTrapFpu: disable trapping FPU instructions to EL2.

SELFOUR-806: aarch32 - Implement lazy FP save/restore

This commit implements lazy FP save/restore mechanism, required for user threads
when they use the FPU. The following caveats take place:

* Only support synchronous exceptions. No support for asynchronous ones.
* VFP opcodes are used instead of normal instructions to discard compiler warnings/errors.
* Support is limited to specific ARM subarchitectures we support and tested this commit on.
* Disable the FPU by default if users are not using it to avoid channels.
* FPU support is not verified yet.
* Will not work properly if using a VM that's running besides other VMs/threads that are using the FPU.

Fix licenses (the rest)

aarch64: FPU lazy context switch