[SK_BUFF]: Introduce skb_reset_network_header(skb)

For the common, open coded 'skb->nh.raw = skb->data' operation, so that we can
later turn skb->nh.raw into a offset, reducing the size of struct sk_buff in
64bit land while possibly keeping it as a pointer on 32bit.

This one touches just the most simple case, next will handle the slightly more
"complex" cases.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ieee80211/ieee80211_rx.c b/net/ieee80211/ieee80211_rx.c
index f39bf7c..be5ffaf 100644
--- a/net/ieee80211/ieee80211_rx.c
+++ b/net/ieee80211/ieee80211_rx.c
@@ -792,7 +792,7 @@
 		skb2->dev = dev;
 		skb2->protocol = __constant_htons(ETH_P_802_3);
 		skb_reset_mac_header(skb2);
-		skb2->nh.raw = skb2->data;
+		skb_reset_network_header(skb2);
 		/* skb2->nh.raw = skb2->data + ETH_HLEN; */
 		dev_queue_xmit(skb2);
 	}