KVM: arm64: Test that SMC64 arch calls are reserved

Assert that the SMC64 view of the Arm architecture range is reserved by
KVM and cannot be filtered by userspace.

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230408121732.3411329-3-oliver.upton@linux.dev