tipc: rename and move message reassembly function

The function tipc_link_frag_rcv() is in reality a re-entrant generic
message reassemby function that has nothing in particular to do with
the link, where it is defined now. This becomes obvious when we see
the need to call the function from other places in the code.

In this commit rename it to tipc_buf_append() and move it to the file
msg.c. We also simplify its signature by moving the tail pointer to
the control block of the head buffer, hence making the head buffer
self-contained.

Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Reviewed-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/tipc/msg.h b/net/tipc/msg.h
index 76d1269..5035119 100644
--- a/net/tipc/msg.h
+++ b/net/tipc/msg.h
@@ -1,7 +1,7 @@
 /*
  * net/tipc/msg.h: Include file for TIPC message header routines
  *
- * Copyright (c) 2000-2007, Ericsson AB
+ * Copyright (c) 2000-2007, 2014, Ericsson AB
  * Copyright (c) 2005-2008, 2010-2011, Wind River Systems
  * All rights reserved.
  *
@@ -711,4 +711,7 @@
 		   u32 destnode);
 int tipc_msg_build(struct tipc_msg *hdr, struct iovec const *msg_sect,
 		   unsigned int len, int max_size, struct sk_buff **buf);
+
+int tipc_buf_append(struct sk_buff **headbuf, struct sk_buff **buf);
+
 #endif