cw1200: drop useless LIST_HEAD

Drop LIST_HEAD where the variable it declares has never
been used.

The semantic patch that fixes this problem is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@
identifier x;
@@
- LIST_HEAD(x);
  ... when != x
// </smpl>

Fixes: a910e4a94f ("cw1200: add driver for the ST-E CW1100 & CW1200 WLAN chipsets")
Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/st/cw1200/queue.c

@@ -283,7 +283,6 @@ int cw1200_queue_put(struct cw1200_queue *queue,
 		     struct cw1200_txpriv *txpriv)
 {
 	int ret = 0;
-	LIST_HEAD(gc_list);
 	struct cw1200_queue_stats *stats = queue->stats;
 
 	if (txpriv->link_id >= queue->stats->map_capacity)