[IPV6]: Remove redundant length check on input

We don't need to check skb->len when we're just about to call
pskb_may_pull since that checks it for us.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/ip6_input.c

@@ -84,14 +84,9 @@ int ipv6_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt
 	 */
 	IP6CB(skb)->iif = skb->dst ? ((struct rt6_info *)skb->dst)->rt6i_idev->dev->ifindex : dev->ifindex;
 
-	if (skb->len < sizeof(struct ipv6hdr))
+	if (unlikely(!pskb_may_pull(skb, sizeof(*hdr))))
 		goto err;
 
-	if (!pskb_may_pull(skb, sizeof(struct ipv6hdr))) {
-		IP6_INC_STATS_BH(IPSTATS_MIB_INHDRERRORS);
-		goto drop;
-	}
-
 	hdr = skb->nh.ipv6h;
 
 	if (hdr->version != 6)