sctp: Adjust PMTU updates to accomodate route invalidation.

This adjusts the call to dst_ops->update_pmtu() so that we can
transparently handle the fact that, in the future, the dst itself can
be invalidated by the PMTU update (when we have non-host routes cached
in sockets).

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sctp/output.c b/net/sctp/output.c
index 539f35d..838e18b 100644
--- a/net/sctp/output.c
+++ b/net/sctp/output.c
@@ -410,7 +410,7 @@
 	if (!sctp_transport_dst_check(tp)) {
 		sctp_transport_route(tp, NULL, sctp_sk(sk));
 		if (asoc && (asoc->param_flags & SPP_PMTUD_ENABLE)) {
-			sctp_assoc_sync_pmtu(asoc);
+			sctp_assoc_sync_pmtu(sk, asoc);
 		}
 	}
 	dst = dst_clone(tp->dst);