[SCTP] Update pmtu handling to be similar to tcp

Introduce new function sctp_transport_update_pmtu that updates
the transports and destination caches view of the path mtu.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Acked-by: Sridhar Samudrala <sri@us.ibm.com>
diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index 5e81984..dc0e70c 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -1006,6 +1006,7 @@
 void sctp_transport_lower_cwnd(struct sctp_transport *, sctp_lower_cwnd_t);
 unsigned long sctp_transport_timeout(struct sctp_transport *);
 void sctp_transport_reset(struct sctp_transport *);
+void sctp_transport_update_pmtu(struct sctp_transport *, u32);
 
 
 /* This is the structure we use to queue packets as they come into