[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/include/net/ip.h b/include/net/ip.h
index 6f7ba32..75f226d 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -46,7 +46,7 @@
 
 static inline unsigned int ip_hdrlen(const struct sk_buff *skb)
 {
-	return skb->nh.iph->ihl * 4;
+	return ip_hdr(skb)->ihl * 4;
 }
 
 struct ipcm_cookie