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/pptp.c b/drivers/net/ppp/pptp.c
index 72b50f5..1c98321 100644
--- a/drivers/net/ppp/pptp.c
+++ b/drivers/net/ppp/pptp.c
@@ -209,7 +209,7 @@
 		}
 		if (skb->sk)
 			skb_set_owner_w(new_skb, skb->sk);
-		kfree_skb(skb);
+		consume_skb(skb);
 		skb = new_skb;
 	}