net: Convert sctp_ctrlsock_ops

These pernet_operations create and destroy net::sctp::ctl_sock.
Since pernet_operations do not send sctp packets each other,
they look safe to be marked as async.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sctp/protocol.c

@@ -1354,6 +1354,7 @@ static void __net_init sctp_ctrlsock_exit(struct net *net)
 static struct pernet_operations sctp_ctrlsock_ops = {
 	.init = sctp_ctrlsock_init,
 	.exit = sctp_ctrlsock_exit,
+	.async = true,
 };
 
 /* Initialize the universe into something sensible.  */