[SK_BUFF]: Introduce skb_set_transport_header

For the cases where the transport header is being set to a offset from
skb->data.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/xfrm6_mode_ro.c

@@ -54,7 +54,7 @@ static int xfrm6_ro_output(struct xfrm_state *x, struct sk_buff *skb)
 
 	hdr_len = x->type->hdr_offset(x, skb, &prevhdr);
 	skb->nh.raw = prevhdr - x->props.header_len;
-	skb->h.raw = skb->data + hdr_len;
+	skb_set_transport_header(skb, hdr_len);
 	memmove(skb->data, iph, hdr_len);
 	return 0;
 }