arm64/sysreg: Add definition for ID_AA64PFR2_EL1

DDI0601 2023-09 defines a new system register ID_AA64PFR2_EL1 which
enumerates FPMR and some new MTE features. Add a definition of this
register.

Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Fuad Tabba <tabba@google.com>
Link: https://lore.kernel.org/r/20231209-b4-arm64-sysreg-additions-v1-5-45284e538474@kernel.org


Signed-off-by: Will Deacon <will@kernel.org>