[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/infiniband/ulp/ipoib/ipoib_cm.c b/drivers/infiniband/ulp/ipoib/ipoib_cm.c
index 2b242a4..c722e5c 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib_cm.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_cm.c
@@ -408,7 +408,7 @@
 	skb_put_frags(skb, IPOIB_CM_HEAD_SIZE, wc->byte_len, newskb);
 
 	skb->protocol = ((struct ipoib_header *) skb->data)->proto;
-	skb->mac.raw = skb->data;
+	skb_reset_mac_header(skb);
 	skb_pull(skb, IPOIB_ENCAP_LEN);
 
 	dev->last_rx = jiffies;
diff --git a/drivers/infiniband/ulp/ipoib/ipoib_ib.c b/drivers/infiniband/ulp/ipoib/ipoib_ib.c
index ba0ee5c..93f7456 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib_ib.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_ib.c
@@ -216,7 +216,7 @@
 	if (wc->slid != priv->local_lid ||
 	    wc->src_qp != priv->qp->qp_num) {
 		skb->protocol = ((struct ipoib_header *) skb->data)->proto;
-		skb->mac.raw = skb->data;
+		skb_reset_mac_header(skb);
 		skb_pull(skb, IPOIB_ENCAP_LEN);
 
 		dev->last_rx = jiffies;