arm64/sysreg: Initial annotation of signed ID registers

We currently annotate a few bitfields as signed in hwcaps, update all of
these to be SignedEnum in the sysreg generation.  Further signed bitfields
can be done incrementally, this is the minimum required for the conversion
of the hwcaps to use token pasting to simplify their declaration.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20221207-arm64-sysreg-helpers-v4-2-25b6b3fb9d18@kernel.org


Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>