KVM: selftests: arm64: Store expected register value in set_id_regs

Rather than comparing against what is returned by the ioctl, store
expected values for the feature ID registers in a table and compare with
that instead.

This will prove useful for subsequent tests involving vCPU reset.

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20240502233529.1958459-6-oliver.upton@linux.dev


Signed-off-by: Marc Zyngier <maz@kernel.org>