virtio_net: disable mac write for virtio 1.0

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>

drivers/net/virtio_net.c

@@ -1030,7 +1030,8 @@ static int virtnet_set_mac_address(struct net_device *dev, void *p)
 				 "Failed to set mac address by vq command.\n");
 			return -EINVAL;
 		}
-	} else if (virtio_has_feature(vdev, VIRTIO_NET_F_MAC)) {
+	} else if (virtio_has_feature(vdev, VIRTIO_NET_F_MAC) &&
+		   !virtio_has_feature(vdev, VIRTIO_F_VERSION_1)) {
 		unsigned int i;
 
 		/* Naturally, this has an atomicity problem. */