[SK_BUFF]: Introduce skb_reset_transport_header(skb)

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

skb->h.raw = skb->data;
skb->h.raw = {skb_push|[__]skb_pull}()

The next ones 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/irda/af_irda.c b/net/irda/af_irda.c
index 0eb7d59..c3cd2ba 100644
--- a/net/irda/af_irda.c
+++ b/net/irda/af_irda.c
@@ -1363,8 +1363,8 @@
 	if (!skb)
 		return err;
 
-	skb->h.raw = skb->data;
-	copied     = skb->len;
+	skb_reset_transport_header(skb);
+	copied = skb->len;
 
 	if (copied > size) {
 		IRDA_DEBUG(2, "%s(), Received truncated frame (%zd < %zd)!\n",