net: Convert nfs_net_ops

These pernet_operations just create and destroy /proc entries
and net_generic()->cb_ident_idr IDR. So, we are able to mark
them async.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

fs/nfs/inode.c

@@ -2122,6 +2122,7 @@ static struct pernet_operations nfs_net_ops = {
 	.exit = nfs_net_exit,
 	.id   = &nfs_net_id,
 	.size = sizeof(struct nfs_net),
+	.async = true,
 };
 
 /*