wireless: zd1211rw: remove redundant assignment of pointer 'q'

Pointer q is initialized and then almost immediately afterwards being
re-assigned the same value. Remove the second redundant assignment.

Cleans up clang warning:
drivers/net/wireless/zydas/zd1211rw/zd_mac.c:503:23: warning: Value
stored to 'q' during its initialization is never read
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/zydas/zd1211rw/zd_mac.c

@@ -509,7 +509,6 @@ void zd_mac_tx_failed(struct urb *urb)
 	int found = 0;
 	int i, position = 0;
 
-	q = &mac->ack_wait_queue;
 	spin_lock_irqsave(&q->lock, flags);
 
 	skb_queue_walk(q, skb) {