tipc: remove an unnecessary NULL check

This is never called with a NULL "buf" and anyway, we dereference 's' on
the lines before so it would Oops before we reach the check.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/subscr.c

@@ -326,7 +326,6 @@ static void tipc_subscrb_rcv_cb(struct net *net, int conid,
 		return tipc_subscrp_cancel(s, subscriber);
 	}
 
-	if (s)
 	tipc_subscrp_subscribe(net, s, subscriber, swap);
 }