PPP: Fix PPP skb leak

[PPP]: Don't leak an sk_buff on interface destruction.
Signed-off-by: G. Liakhovetski <gl@dsa-ac.de>
Acked-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/net/ppp_generic.c

@@ -2544,6 +2544,9 @@ static void ppp_destroy_interface(struct ppp *ppp)
 	ppp->active_filter = NULL;
 #endif /* CONFIG_PPP_FILTER */
 
+	if (ppp->xmit_pending)
+		kfree_skb(ppp->xmit_pending);
+
 	kfree(ppp);
 }