[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/ieee80211/ieee80211_rx.c b/net/ieee80211/ieee80211_rx.c
index 2b85494..59a765c 100644
--- a/net/ieee80211/ieee80211_rx.c
+++ b/net/ieee80211/ieee80211_rx.c
@@ -595,7 +595,7 @@
 		if (frag != 0)
 			flen -= hdrlen;
 
-		if (skb_tail_pointer(frag_skb) + flen > frag_skb->end) {
+		if (frag_skb->tail + flen > frag_skb->end) {
 			printk(KERN_WARNING "%s: host decrypted and "
 			       "reassembled frame did not fit skb\n",
 			       dev->name);