[SK_BUFF]: Introduce skb_transport_header(skb)

For the places where we need a pointer to the transport header, it is
still legal to touch skb->h.raw directly if just adding to,
subtracting from or setting it to another layer header.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/ipx.h b/include/net/ipx.h
index c6b2ee6..4cc0b4e 100644
--- a/include/net/ipx.h
+++ b/include/net/ipx.h
@@ -43,7 +43,7 @@
 
 static __inline__ struct ipxhdr *ipx_hdr(struct sk_buff *skb)
 {
-	return (struct ipxhdr *)skb->h.raw;
+	return (struct ipxhdr *)skb_transport_header(skb);
 }
 
 struct ipx_interface {