net: sched: fix error return code in tcf_del_walker()

When nla_put_u32() fails, 'ret' could be 0, it should
return error code in tcf_del_walker().
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/act_api.c

@@ -381,7 +381,8 @@ static int tcf_del_walker(struct tcf_idrinfo *idrinfo, struct sk_buff *skb,
 	}
 	mutex_unlock(&idrinfo->lock);
 
-	if (nla_put_u32(skb, TCA_FCNT, n_i))
+	ret = nla_put_u32(skb, TCA_FCNT, n_i);
+	if (ret)
 		goto nla_put_failure;
 	nla_nest_end(skb, nest);