arm64/sysreg: Allow enumerations to be declared as signed or unsigned

arm64/sysreg: Allow enumerations to be declared as signed or unsigned

Many of our enumerations follow a standard scheme where the values can be
treated as signed however there are some where the value must be treated
as signed and others that are simple enumerations where there is no clear
ordering to the values. Provide new field types SignedEnum and
UnsignedEnum which allows the signedness to be specified in the sysreg
definition and emit a REG_FIELD_SIGNED define for these which is a
boolean corresponding to our current FTR_UNSIGNED and FTR_SIGNED macros.

Existing Enums will need to be converted, since these do not have a
define generated anyone wishing to use the sign of one of these will
need to explicitly annotate that field so nothing should start going
wrong by default.

Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20221207-arm64-sysreg-helpers-v4-1-25b6b3fb9d18@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>