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.
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.
Now these bitfield definitions are generated from the same source file
in the kernel and libsel4, and also result in the same include path: <sel4/shared_types_gen.h>
The definitions of guard and badge sizes is going to be changed for 64-bit platforms,
this change provides an easy way of providing different definitions
