ath9k_htc: Lock sta_notify() callback

Since ->sta_notify() can sleep, protect
the callback with a mutex.

Signed-off-by: Sujith <Sujith.Manoharan@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

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

@@ -1452,6 +1452,8 @@ static void ath9k_htc_sta_notify(struct ieee80211_hw *hw,
 	struct ath9k_htc_priv *priv = hw->priv;
 	int ret;
 
+	mutex_lock(&priv->mutex);
+
 	switch (cmd) {
 	case STA_NOTIFY_ADD:
 		ret = ath9k_htc_add_station(priv, vif, sta);
@@ -1464,6 +1466,8 @@ static void ath9k_htc_sta_notify(struct ieee80211_hw *hw,
 	default:
 		break;
 	}
+
+	mutex_unlock(&priv->mutex);
 }
 
 static int ath9k_htc_conf_tx(struct ieee80211_hw *hw, u16 queue,