use skb_end_offset() in skb_try_coalesce()

Commit ec47ea82(skb: Add inline helper for getting the skb end offset from
head) introduces this helper function, skb_end_offset(),
we should make use of it.
Signed-off-by: NWeiping Pan <wpan@redhat.com>
Acked-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/skbuff.c

@@ -3483,8 +3483,7 @@ bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from,
 		    skb_shinfo(from)->nr_frags > MAX_SKB_FRAGS)
 			return false;
 
-		delta = from->truesize -
-			SKB_TRUESIZE(skb_end_pointer(from) - from->head);
+		delta = from->truesize - SKB_TRUESIZE(skb_end_offset(from));
 	}
 
 	WARN_ON_ONCE(delta < len);