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.

arm: make mode reserved regions a constant

Replace an unneccessary function call with a constant. This simplifies
and increases the maintainability of arch_init_freemem.

aarch64: adjustments to pass c-parser

This commit updates the aarch64 build to pass the c-parser.

- replace 0b constants with decimal
- remove empty array definition
- replace __uint128_t with uint64_t, and double the array size
- remove variable shadowing

No further verification guarantees are provided for aarch64 code.

style: consistently align pointer with name

Run astyle with align-pointer=name

Upgrade to astyle 3.1

This produces minor changes

Update init_freemem to check for mode dependant reserve regions

aarch64: Initial implementation

ARM: Move vspace.h to mode specific folder