arm64/hwcap: Add support for FEAT_RPRFM

FEAT_RPRFM adds a new range prefetch hint within the existing PRFM space
for range prefetch hinting. Add a new hwcap to allow userspace to discover
support for the new instruction.

Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20221017152520.1039165-4-broonie@kernel.org


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