[SK_BUFF]: Introduce skb_transport_offset()

For the quite common 'skb->h.raw - skb->data' sequence.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/cxgb3/sge.c b/drivers/net/cxgb3/sge.c
index a891f6f..d38b1bc 100644
--- a/drivers/net/cxgb3/sge.c
+++ b/drivers/net/cxgb3/sge.c
@@ -1319,9 +1319,10 @@
 	/* Only TX_DATA builds SGLs */
 
 	from = (struct work_request_hdr *)skb->data;
-	memcpy(&d->flit[1], &from[1], skb->h.raw - skb->data - sizeof(*from));
+	memcpy(&d->flit[1], &from[1],
+	       skb_transport_offset(skb) - sizeof(*from));
 
-	flits = (skb->h.raw - skb->data) / 8;
+	flits = skb_transport_offset(skb) / 8;
 	sgp = ndesc == 1 ? (struct sg_ent *)&d->flit[flits] : sgl;
 	sgl_flits = make_sgl(skb, sgp, skb->h.raw, skb->tail - skb->h.raw,
 			     adap->pdev);
@@ -1349,7 +1350,7 @@
 	if (skb->len <= WR_LEN && cnt == 0)
 		return 1;	/* packet fits as immediate data */
 
-	flits = (skb->h.raw - skb->data) / 8;	/* headers */
+	flits = skb_transport_offset(skb) / 8;	/* headers */
 	if (skb->tail != skb->h.raw)
 		cnt++;
 	return flits_to_desc(flits + sgl_len(cnt));