pkt_sched: Fix handling of gso skbs on requeuing

Jay Cliburn noticed and diagnosed a bug triggered in
dev_gso_skb_destructor() after last change from qdisc->gso_skb
to qdisc->requeue list. Since gso_segmented skbs can't be queued
to another list this patch brings back qdisc->gso_skb for them.

Reported-by: Jay Cliburn <jcliburn@gmail.com>
Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/sch_generic.h

@@ -52,6 +52,7 @@ struct Qdisc
 	u32			parent;
 	atomic_t		refcnt;
 	unsigned long		state;
+	struct sk_buff		*gso_skb;
 	struct sk_buff_head	requeue;
 	struct sk_buff_head	q;
 	struct netdev_queue	*dev_queue;