kselftest/arm64: Add FEAT_RPRFM to the hwcap test

Since the newly added instruction is in the HINT space we can't reasonably
test for it actually being present.

Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20221017152520.1039165-5-broonie@kernel.org


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