wext: unregister_pernet_subsys() on notifier registration failure

If register_netdevice_notifier() fails (which in practice it can't
right now), we should call unregister_pernet_subsys(). Do that.
Reported-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/wext-core.c

@@ -399,7 +399,10 @@ static int __init wireless_nlevent_init(void)
 	if (err)
 		return err;
 
-	return register_netdevice_notifier(&wext_netdev_notifier);
+	err = register_netdevice_notifier(&wext_netdev_notifier);
+	if (err)
+		unregister_pernet_subsys(&wext_pernet_ops);
+	return err;
 }
 
 subsys_initcall(wireless_nlevent_init);