arm64: cpufeature: use cpucap naming

arm64: cpufeature: use cpucap naming

To more clearly align the various users of the cpucap enumeration, this patch
changes the cpufeature code to use the term `cpucap` in favour of `cpu_hwcap`.
This more clearly aligns with other users of the cpucaps, and avoids confusion
with the ELF hwcaps.

There should be no functional change as a result of this patch; this is
purely a renaming exercise.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20230607164846.3967305-4-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>