KVM: arm64: selftest: Add standalone test checking for KVM's own UUID

Tinkering with UUIDs is a perilious task, and the KVM UUID gets
broken at times. In order to spot this early enough, add a selftest
that will shout if the expected value isn't found.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Sebastian Ott <sebott@redhat.com>
Link: https://lore.kernel.org/r/20250721130558.50823-1-jackabt.amazon@gmail.com
Link: https://lore.kernel.org/r/20250806171341.1521210-1-maz@kernel.org


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