kselftest/arm64: add MOPS to hwcap test

Add the MOPS hwcap to the hwcap kselftest and check that a SIGILL is not
generated when the feature is detected. A SIGILL is reliable when the
feature is not detected as SCTLR_EL1.MSCEn won't have been set.

Reviewed-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>