rt2x00: Make use of ieee80211_free_txskb in tx path

ieee80211_free_txskb should be used when dropping a frame in the device
rx path such that mac80211 knows about this frame being dropped.

Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
Acked-by: Gertjan van Wingerde <gwingerde@gmail.com>
Acked-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rt2x00/rt2x00mac.c

@@ -160,7 +160,7 @@ void rt2x00mac_tx(struct ieee80211_hw *hw, struct sk_buff *skb)
  exit_fail:
 	rt2x00queue_pause_queue(queue);
  exit_free_skb:
-	dev_kfree_skb_any(skb);
+	ieee80211_free_txskb(hw, skb);
 }
 EXPORT_SYMBOL_GPL(rt2x00mac_tx);