tipc: Fix kfree_skb() of uninitialised pointer

Commit 7098356b ("tipc: fix error handling of expanding buffer
headroom") added a "goto tx_error".  This is fine upstream, but
when backported to 4.3 it results in attempting to free the clone
before it has been allocated.  In this early error case, no
cleanup is needed.
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

net/tipc/udp_media.c

@@ -162,7 +162,7 @@ static int tipc_udp_send_msg(struct net *net, struct sk_buff *skb,
 	if (skb_headroom(skb) < UDP_MIN_HEADROOM) {
 		err = pskb_expand_head(skb, UDP_MIN_HEADROOM, 0, GFP_ATOMIC);
 		if (err)
-			goto tx_error;
+			return err;
 	}
 
 	clone = skb_clone(skb, GFP_ATOMIC);