arm64/sysreg: Standardise naming of ID_AA64MMFR0_EL1.BigEnd

arm64/sysreg: Standardise naming of ID_AA64MMFR0_EL1.BigEnd

For some reason we refer to ID_AA64MMFR0_EL1.BigEnd as BIGENDEL. Remove the
EL from the name, bringing the naming into sync with DDI0487H.a. Due to the
large amount of MixedCase in this register which isn't really consistent
with either the kernel style or the majority of the architecture the use of
upper case is preserved. No functional changes.

Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Kristina Martsenko <kristina.martsenko@arm.com>
Link: https://lore.kernel.org/r/20220905225425.1871461-9-broonie@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>