ifb: fix oops when loading the ifb failed

If __rtnl_link_register() return faild when loading the ifb, it will
take the wrong path and get oops, so fix it just like dummy.

Signed-off-by: Ding Tianhong <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/ifb.c

···
 
 	rtnl_lock();
 	err = __rtnl_link_register(&ifb_link_ops);
+	if (err < 0)
+		goto out;
 
 	for (i = 0; i < numifbs && !err; i++) {
 		err = ifb_init_one(i);
···
 	}
 	if (err)
 		__rtnl_link_unregister(&ifb_link_ops);
+
+out:
 	rtnl_unlock();
 
 	return err;