[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/net/atm/br2684.c b/net/atm/br2684.c
index c444f5e..900d42c 100644
--- a/net/atm/br2684.c
+++ b/net/atm/br2684.c
@@ -458,7 +458,7 @@
 	/* FIXME: tcpdump shows that pointer to mac header is 2 bytes earlier,
 	   than should be. What else should I set? */
 	skb_pull(skb, plen);
-	skb->mac.raw = ((char *) (skb->data)) - ETH_HLEN;
+	skb->mac.raw = skb->data - ETH_HLEN;
 	skb->pkt_type = PACKET_HOST;
 #ifdef CONFIG_BR2684_FAST_TRANS
 	skb->protocol = ((u16 *) skb->data)[-1];
diff --git a/net/atm/clip.c b/net/atm/clip.c
index 8c38258..ccba24f 100644
--- a/net/atm/clip.c
+++ b/net/atm/clip.c
@@ -213,7 +213,7 @@
 		return;
 	}
 	ATM_SKB(skb)->vcc = vcc;
-	skb->mac.raw = skb->data;
+	skb_reset_mac_header(skb);
 	if (!clip_vcc->encap
 	    || skb->len < RFC1483LLC_LEN
 	    || memcmp(skb->data, llc_oui, sizeof (llc_oui)))