arm64/sysreg: Describe ID_AA64SMFR0_EL1.SMEVer as an enumeration

As with the corresponding SVE field ID_AA64ZFR0_EL1.SVEVer and other ID
register fields the SMEVer field should be identified as an enumeration
but it is currently described as a plain field (most likely due to there
presently being only one possible value). Update it to be an enumeration
as one would expect. No functional change.
Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Kristina Martsenko <kristina.martsenko@arm.com>
Link: https://lore.kernel.org/r/20220905225425.1871461-3-broonie@kernel.orgSigned-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/tools/sysreg

@@ -98,7 +98,9 @@ Enum	63	FA64
 	0b1	IMP
 EndEnum
 Res0	62:60
-Field	59:56	SMEver
+Enum	59:56	SMEver
+	0b0000	IMP
+EndEnum
 Enum	55:52	I16I64
 	0b0000	NI
 	0b1111	IMP