arm64/sysreg: Standardise naming for ID_AA64MMFR2_EL1.CnP

arm64/sysreg: Standardise naming for ID_AA64MMFR2_EL1.CnP

The kernel refers to ID_AA64MMFR2_EL1.CnP as CNP. In preparation for
automatic generation of defines for the system registers bring the naming
used by the kernel in sync with that of DDI0487H.a. 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/20220905225425.1871461-13-broonie@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>