[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>
diff --git a/drivers/net/sb1000.c b/drivers/net/sb1000.c
index b9fa4fb..1de3eec 100644
--- a/drivers/net/sb1000.c
+++ b/drivers/net/sb1000.c
@@ -834,7 +834,7 @@
 			goto dropped_frame;
 		}
 		skb->dev = dev;
-		skb->mac.raw = skb->data;
+		skb_reset_mac_header(skb);
 		skb->protocol = (unsigned short) buffer[NewDatagramHeaderSkip + 16];
 		insw(ioaddr, skb_put(skb, NewDatagramDataSize),
 			NewDatagramDataSize / 2);