[SK_BUFF]: Introduce skb_reset_mac_header(skb)

For the common, open coded 'skb->mac.raw = skb->data' operation, so that we can
later turn skb->mac.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>

drivers/net/appletalk/cops.c

@@ -853,7 +853,7 @@ static void cops_rx(struct net_device *dev)
                 return;
         }
 
-        skb->mac.raw    = skb->data;    /* Point to entire packet. */
+        skb_reset_mac_header(skb);    /* Point to entire packet. */
         skb_pull(skb,3);
         skb->h.raw      = skb->data;    /* Point to data (Skip header). */
 

drivers/net/appletalk/ltpc.c

@@ -770,7 +770,7 @@ static int sendup_buffer (struct net_device *dev)
 	skb->data[0] = dnode;
 	skb->data[1] = snode;
 	skb->data[2] = llaptype;
-	skb->mac.raw = skb->data;	/* save pointer to llap header */
+	skb_reset_mac_header(skb);	/* save pointer to llap header */
 	skb_pull(skb,3);
 
 	/* copy ddp(s,e)hdr + contents */