net: Convert genl_pernet_ops

This pernet_operations create and destroy net::genl_sock.
Foreign pernet_operations don't touch it.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Acked-by: Andrei Vagin <avagin@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/netlink/genetlink.c

@@ -1035,6 +1035,7 @@ static void __net_exit genl_pernet_exit(struct net *net)
 static struct pernet_operations genl_pernet_ops = {
 	.init = genl_pernet_init,
 	.exit = genl_pernet_exit,
+	.async = true,
 };
 
 static int __init genl_init(void)