net: Convert fou_net_ops

These pernet_operations initialize and destroy
pernet net_generic(net, fou_net_id) list.
The rest of net_generic(net, fou_net_id) accesses
may happen after netlink message, and in-tree
pernet_operations do not send FOU_GENL_NAME messages.
So, these pernet_operations are safe to be marked
as async.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/fou.c

@@ -1081,6 +1081,7 @@ static struct pernet_operations fou_net_ops = {
 	.exit = fou_exit_net,
 	.id   = &fou_net_id,
 	.size = sizeof(struct fou_net),
+	.async = true,
 };
 
 static int __init fou_init(void)