KVM: selftests: get-reg-list: support ID register features

This stops the test complaining about missing registers, when running
on an older kernel that does not support newer features.

Signed-off-by: Joey Gouly <joey.gouly@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Oliver Upton <oliver.upton@linux.dev>
Cc: Mark Brown <broonie@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Link: https://lore.kernel.org/r/20230606145859.697944-20-joey.gouly@arm.com


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