[SK_BUFF]: Convert skb->end to sk_buff_data_t

Now to convert the last one, skb->data, that will allow many simplifications
and removal of some of the offset helpers.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index fdb6eb1..50dc5ed 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -785,7 +785,7 @@
 
 	skb_orphan(skb);
 
-	delta = skb->end - skb_tail_pointer(skb);
+	delta = skb->end - skb->tail;
 	if (delta * 2 < skb->truesize)
 		return skb;