tipc: Minor optimization to topology service connection establishment

Eliminates a local iovec structure containing no data, which was
previously used during the establishment of a topology service connection,
since the same effect can be achieved by passing in a NULL pointer and
an iovec length of zero.
Signed-off-by: Allan Stephens <Allan.Stephens@windriver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

net/tipc/subscr.c

@@ -472,8 +472,6 @@ static void subscr_named_msg_event(void *usr_handle,
 				   struct tipc_portid const *orig,
 				   struct tipc_name_seq const *dest)
 {
-	static struct iovec msg_sect = {NULL, 0};
-
 	struct subscriber *subscriber;
 	u32 server_port_ref;
 
@@ -523,7 +521,7 @@ static void subscr_named_msg_event(void *usr_handle,
 
 	/* Send an ACK- to complete connection handshaking */
 
-	tipc_send(server_port_ref, 1, &msg_sect);
+	tipc_send(server_port_ref, 0, NULL);
 
 	/* Handle optional subscription request */