rtlwifi: rtl8192cu: Fix unitialized struct

Driver rtl8192cu assigns a new struct rtl_tcb_desc object, but fails to
clear it.
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Stable <stable@kernel.org>  [2.6.39+]
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rtlwifi/usb.c

@@ -863,6 +863,7 @@ static void _rtl_usb_tx_preprocess(struct ieee80211_hw *hw, struct sk_buff *skb,
 	u8 tid = 0;
 	u16 seq_number = 0;
 
+	memset(&tcb_desc, 0, sizeof(struct rtl_tcb_desc));
 	if (ieee80211_is_auth(fc)) {
 		RT_TRACE(rtlpriv, COMP_SEND, DBG_DMESG, ("MAC80211_LINKING\n"));
 		rtl_ips_nic_on(hw);