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

arch/arm64/tools/sysreg

@@ -846,12 +846,12 @@ Enum	27:24	GIC
 	0b0001	IMP
 	0b0010	V4P1
 EndEnum
-Enum	23:20	AdvSIMD
+SignedEnum	23:20	AdvSIMD
 	0b0000	IMP
 	0b0001	FP16
 	0b1111	NI
 EndEnum
-Enum	19:16	FP
+SignedEnum	19:16	FP
 	0b0000	IMP
 	0b0001	FP16
 	0b1111	NI