tipc: Message rejection rework preparatory changes

This patch defines a few new message header manipulation routines,
and generalizes the usefulness of another, in preparation for upcoming
rework of TIPC's message rejection code.

Signed-off-by: Allan Stephens <allan.stephens@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/tipc/discover.c b/net/tipc/discover.c
index 64c2028..1657f0e 100644
--- a/net/tipc/discover.c
+++ b/net/tipc/discover.c
@@ -121,7 +121,7 @@
 	if (buf) {
 		msg = buf_msg(buf);
 		msg_init(msg, LINK_CONFIG, type, DSC_H_SIZE, dest_domain);
-		msg_set_non_seq(msg);
+		msg_set_non_seq(msg, 1);
 		msg_set_req_links(msg, req_links);
 		msg_set_dest_domain(msg, dest_domain);
 		msg_set_bc_netid(msg, tipc_net_id);