KVM: arm64: selftests: get-reg-list: Simplify feature dependency

Describing the dependencies between registers and features is on
the masochistic side of things, with hard-coded values that would
be better taken from the existing description.

Add a couple of helpers to that effect, and repaint the dependency
array. More could be done to improve this test, but my interest is
wearing  thin...

Signed-off-by: Marc Zyngier <maz@kernel.org>
Tested-by: Itaru Kitayama <itaru.kitayama@fujitsu.com>
Link: https://lore.kernel.org/r/20250714122634.3334816-10-maz@kernel.org


Signed-off-by: Oliver Upton <oliver.upton@linux.dev>