arm64/sysreg: Standardise naming for MTE feature enumeration

In preparation for conversion to automatic generation refresh the names
given to the items in the MTE feture enumeration to reflect our standard
pattern for naming, corresponding to the architecture feature names they
reflect. 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/20220905225425.1871461-17-broonie@kernel.org


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