ath9k: Fix TX poll cancelling

In ath9k_stop(), tx_complete_work was being cancelled twice.
This patch fixes it. Also, locking sc->mutex should be done
at the beginning.
Signed-off-by: NSujith <Sujith.Manoharan@atheros.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/main.c

@@ -2105,6 +2105,8 @@ static void ath9k_stop(struct ieee80211_hw *hw)
 	struct ath_wiphy *aphy = hw->priv;
 	struct ath_softc *sc = aphy->sc;
 
+	mutex_lock(&sc->mutex);
+
 	aphy->state = ATH_WIPHY_INACTIVE;
 
 	cancel_delayed_work_sync(&sc->ath_led_blink_work);
@@ -2117,13 +2119,10 @@ static void ath9k_stop(struct ieee80211_hw *hw)
 
 	if (sc->sc_flags & SC_OP_INVALID) {
 		DPRINTF(sc, ATH_DBG_ANY, "Device not present\n");
+		mutex_unlock(&sc->mutex);
 		return;
 	}
 
-	mutex_lock(&sc->mutex);
-
-	cancel_delayed_work_sync(&sc->tx_complete_work);
-
 	if (ath9k_wiphy_started(sc)) {
 		mutex_unlock(&sc->mutex);
 		return; /* another wiphy still in use */