rtlwifi: usb: add missing freeing of skbuff

Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>
Acked-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: stable@vger.kernel.org
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rtlwifi/usb.c

@@ -851,6 +851,7 @@ static void _rtl_usb_transmit(struct ieee80211_hw *hw, struct sk_buff *skb,
 	if (unlikely(!_urb)) {
 		RT_TRACE(rtlpriv, COMP_ERR, DBG_EMERG,
 			 "Can't allocate urb. Drop skb!\n");
+		kfree_skb(skb);
 		return;
 	}
 	_rtl_submit_tx_urb(hw, _urb);