[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/packet/af_packet.c b/net/packet/af_packet.c
index 73cb2d3..1225e75 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -401,14 +401,14 @@
 	 * notable one here. This should really be fixed at the driver level.
 	 */
 	skb_reserve(skb, LL_RESERVED_SPACE(dev));
-	skb->nh.raw = skb->data;
+	skb_reset_network_header(skb);
 
 	/* Try to align data part correctly */
 	if (dev->hard_header) {
 		skb->data -= dev->hard_header_len;
 		skb->tail -= dev->hard_header_len;
 		if (len < dev->hard_header_len)
-			skb->nh.raw = skb->data;
+			skb_reset_network_header(skb);
 	}
 
 	/* Returns -EFAULT on error */
@@ -768,7 +768,7 @@
 		goto out_unlock;
 
 	skb_reserve(skb, LL_RESERVED_SPACE(dev));
-	skb->nh.raw = skb->data;
+	skb_reset_network_header(skb);
 
 	if (dev->hard_header) {
 		int res;