rt2x00: Add kill_tx_queue callback function

provide rt2x00lib the possibility to kill a particular TX queue.
This can be useful when disabling the radio, but more importantly
will allow beaconing to be disabled when mac80211 requests this
(during scanning for example)

Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/rt2x00/rt73usb.c b/drivers/net/wireless/rt2x00/rt73usb.c
index f854551..24e97b3 100644
--- a/drivers/net/wireless/rt2x00/rt73usb.c
+++ b/drivers/net/wireless/rt2x00/rt73usb.c
@@ -2293,6 +2293,7 @@
 	.write_beacon		= rt73usb_write_beacon,
 	.get_tx_data_len	= rt73usb_get_tx_data_len,
 	.kick_tx_queue		= rt73usb_kick_tx_queue,
+	.kill_tx_queue		= rt2x00usb_kill_tx_queue,
 	.fill_rxdone		= rt73usb_fill_rxdone,
 	.config_shared_key	= rt73usb_config_shared_key,
 	.config_pairwise_key	= rt73usb_config_pairwise_key,