rtlwifi: Fix the usage of the wrong variable in usb.c

In routine _rtl_rx_pre_process(), skb_dequeue() is called to get an skb;
however, the wrong variable name is used in subsequent calls.
Reported-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Stable <stable@vger.kernel.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rtlwifi/usb.c

@@ -542,8 +542,8 @@ static void _rtl_rx_pre_process(struct ieee80211_hw *hw, struct sk_buff *skb)
 	WARN_ON(skb_queue_empty(&rx_queue));
 	while (!skb_queue_empty(&rx_queue)) {
 		_skb = skb_dequeue(&rx_queue);
-		_rtl_usb_rx_process_agg(hw, skb);
-		ieee80211_rx_irqsafe(hw, skb);
+		_rtl_usb_rx_process_agg(hw, _skb);
+		ieee80211_rx_irqsafe(hw, _skb);
 	}
 }