wl3501_cs: Add spinlock to wl3501_reset

Likely wl3501_reset should acquire spinlock as wl3501_{open, close}.
One of calls of wl3501_reset has been already protected.
The others were unprotected and might lead to a race condition.
The patch adds spinlock into the wl3501_reset and removes it from
wl3501_tx_timeout.

Found by Linux Driver Verification project (linuxtesting.org)
Signed-off-by: Pavel Andrianov <andrianov@ispras.ru>
Acked-by: Vaishali Thakkar <vaishali.thakkar@oracle.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/wl3501_cs.c

@@ -1258,7 +1258,9 @@ static int wl3501_reset(struct net_device *dev)
 {
 	struct wl3501_card *this = netdev_priv(dev);
 	int rc = -ENODEV;
+	unsigned long flags;
 
+	spin_lock_irqsave(&this->lock, flags);
 	wl3501_block_interrupt(this);
 
 	if (wl3501_init_firmware(this)) {
@@ -1280,20 +1282,17 @@ static int wl3501_reset(struct net_device *dev)
 	pr_debug("%s: device reset", dev->name);
 	rc = 0;
 out:
+	spin_unlock_irqrestore(&this->lock, flags);
 	return rc;
 }
 
 static void wl3501_tx_timeout(struct net_device *dev)
 {
-	struct wl3501_card *this = netdev_priv(dev);
 	struct net_device_stats *stats = &dev->stats;
-	unsigned long flags;
 	int rc;
 
 	stats->tx_errors++;
-	spin_lock_irqsave(&this->lock, flags);
 	rc = wl3501_reset(dev);
-	spin_unlock_irqrestore(&this->lock, flags);
 	if (rc)
 		printk(KERN_ERR "%s: Error %d resetting card on Tx timeout!\n",
 		       dev->name, rc);