pkt_sched: Move gso_skb into Qdisc.

We liberate any dangling gso_skb during qdisc destruction.

It really only matters for the root qdisc.  But when qdiscs
can be shared by multiple netdev_queue objects, we can't
have the gso_skb in the netdev_queue any more.

Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/sch_generic.h

@@ -36,6 +36,7 @@ struct Qdisc
 	u32			handle;
 	u32			parent;
 	atomic_t		refcnt;
+	struct sk_buff		*gso_skb;
 	struct sk_buff_head	q;
 	struct netdev_queue	*dev_queue;
 	struct list_head	list;