[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/dccp.h b/include/linux/dccp.h
index 1cb054b..1f4df61 100644
--- a/include/linux/dccp.h
+++ b/include/linux/dccp.h
@@ -265,9 +265,9 @@
 
 static inline struct dccp_hdr *dccp_zeroed_hdr(struct sk_buff *skb, int headlen)
 {
-	skb->h.raw = skb_push(skb, headlen);
-	memset(skb->h.raw, 0, headlen);
-	return dccp_hdr(skb);
+	skb_push(skb, headlen);
+	skb_reset_transport_header(skb);
+	return memset(skb->h.raw, 0, headlen);
 }
 
 static inline struct dccp_hdr_ext *dccp_hdrx(const struct sk_buff *skb)