[SK_BUFF]: Introduce ip_hdr(), remove skb->nh.iph

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/r8169.c b/drivers/net/r8169.c
index 34280f9..45876a8 100644
--- a/drivers/net/r8169.c
+++ b/drivers/net/r8169.c
@@ -2284,7 +2284,7 @@
 			return LargeSend | ((mss & MSSMask) << MSSShift);
 	}
 	if (skb->ip_summed == CHECKSUM_PARTIAL) {
-		const struct iphdr *ip = skb->nh.iph;
+		const struct iphdr *ip = ip_hdr(skb);
 
 		if (ip->protocol == IPPROTO_TCP)
 			return IPCS | TCPCS;