Revert "sit: reload iphdr in ipip6_rcv"

This reverts commit b699d003.

As per Eric Dumazet, the pskb_may_pull() is a NOP in this
particular case, so the 'iph' reload is unnecessary.
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/sit.c

@@ -657,7 +657,6 @@ static int ipip6_rcv(struct sk_buff *skb)
 		if (iptunnel_pull_header(skb, 0, htons(ETH_P_IPV6),
 		    !net_eq(tunnel->net, dev_net(tunnel->dev))))
 			goto out;
-		iph = ip_hdr(skb);
 
 		err = IP_ECN_decapsulate(iph, skb);
 		if (unlikely(err)) {