pptp: fix skb leak in pptp_xmit()

In case we cant transmit skb, we must free it

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Dmitry Kozlov <xeb@mail.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/pptp.c

@@ -285,8 +285,10 @@ static int pptp_xmit(struct ppp_channel *chan, struct sk_buff *skb)
 	ip_send_check(iph);
 
 	ip_local_out(skb);
+	return 1;
 
 tx_error:
+	kfree_skb(skb);
 	return 1;
 }