net/sched: remove redundant null check on head

head is previously null checked and so the 2nd null check on head
is redundant and therefore can be removed.

Detected by CoverityScan, CID#1399505 ("Logically dead code")
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Acked-by: NJiri Pirko <jiri@mellanox.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/sched/cls_matchall.c

@@ -203,8 +203,7 @@ static int mall_change(struct net *net, struct sk_buff *in_skb,
 
 	*arg = (unsigned long) head;
 	rcu_assign_pointer(tp->root, new);
-	if (head)
-		call_rcu(&head->rcu, mall_destroy_rcu);
+	call_rcu(&head->rcu, mall_destroy_rcu);
 	return 0;
 
 err_replace_hw_filter: