kselftest/arm64: pac: Fix skipping of tests on systems without PAC

The PAC tests check to see if the system supports the relevant PAC features
but instead of skipping the tests if they can't be executed they fail the
tests which makes things look like they're not working when they are.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20210819165723.43903-1-broonie@kernel.org


Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>