pkt_sched: Kill set but unused variable 'protocol' in tc_classify()

I checked the history and this has been like this since the
beginning of time.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/sched/sch_api.c

@@ -1673,10 +1673,8 @@ int tc_classify(struct sk_buff *skb, struct tcf_proto *tp,
 {
 	int err = 0;
 #ifdef CONFIG_NET_CLS_ACT
-	__be16 protocol;
 	struct tcf_proto *otp = tp;
 reclassify:
-	protocol = skb->protocol;
 #endif
 
 	err = tc_classify_compat(skb, tp, res);