[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/include/linux/skbuff.h b/include/linux/skbuff.h
index 31806a7..7c1f175 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -957,6 +957,11 @@
 	skb->tail += len;
 }
 
+static inline void skb_reset_transport_header(struct sk_buff *skb)
+{
+	skb->h.raw = skb->data;
+}
+
 static inline unsigned char *skb_network_header(const struct sk_buff *skb)
 {
 	return skb->nh.raw;