The spec states that mac in config space is only driver-writable in the
legacy case. Fence writing it in virtnet_set_mac_address() in the
virtio 1.0 case.
Suggested-by: Cornelia Huck <cornelia.huck@de.ibm.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>