net: Convert sctp_defaults_ops

These pernet_operations have a deal with sysctl, /proc
entries and statistics. Also, there are freeing of
net::sctp::addr_waitq queue and net::sctp::local_addr_list
in exit method. All of them look pernet-divided, and it
seems these items are only interesting for sctp_defaults_ops,
which are safe to be executed in parallel.
Signed-off-by: NKirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/sctp/protocol.c

@@ -1330,6 +1330,7 @@ static void __net_exit sctp_defaults_exit(struct net *net)
 static struct pernet_operations sctp_defaults_ops = {
 	.init = sctp_defaults_init,
 	.exit = sctp_defaults_exit,
+	.async = true,
 };
 
 static int __net_init sctp_ctrlsock_init(struct net *net)