ppp: avoid false drop_monitor false positives

Call consume_skb() in place of kfree_skb() were appropriate.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ppp/ppp_async.c b/drivers/net/ppp/ppp_async.c
index af95a98..a031f6b 100644
--- a/drivers/net/ppp/ppp_async.c
+++ b/drivers/net/ppp/ppp_async.c
@@ -613,7 +613,7 @@
 	*buf++ = PPP_FLAG;
 	ap->olim = buf;
 
-	kfree_skb(ap->tpkt);
+	consume_skb(ap->tpkt);
 	ap->tpkt = NULL;
 	return 1;
 }