ar9170: remove unneeded flush_workqueue()

cancel_delayed_work_sync() and cancel_work_sync() are already being
used therefore already waiting for all pending work by the driver
to have been completed, no need to flush the mac80211 workqueue.

Cc: Christian Lamparter <chunkeey@web.de>
Signed-off-by: NLuis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ar9170/main.c

@@ -1290,14 +1290,13 @@ static void ar9170_op_stop(struct ieee80211_hw *hw)
 	if (IS_STARTED(ar))
 		ar->state = AR9170_IDLE;
 
-	flush_workqueue(ar->hw->workqueue);
-
 	cancel_delayed_work_sync(&ar->tx_janitor);
 #ifdef CONFIG_AR9170_LEDS
 	cancel_delayed_work_sync(&ar->led_work);
 #endif
 	cancel_work_sync(&ar->filter_config_work);
 	cancel_work_sync(&ar->beacon_work);
+
 	mutex_lock(&ar->mutex);
 
 	if (IS_ACCEPTING_CMD(ar)) {