6LoWPAN: double free in lowpan_fragment_xmit()

dev_queue_xmit() consumes its own skb, so the call to dev_kfree_skb()
in lowpan_fragment_xmit() is a double free.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Alexander Smirnov <alex.bluesman.smirnov@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ieee802154/6lowpan.c

@@ -980,9 +980,6 @@ lowpan_fragment_xmit(struct sk_buff *skb, u8 *head,
 
 	ret = dev_queue_xmit(frag);
 
-	if (ret < 0)
-		dev_kfree_skb(frag);
-
 	return ret;
 }