iwlwifi: add debug messages when start aggregation queue

This patch adding few more debug messages if encounter error when driver
try to start tx aggregation queue. Also change from IWL_ERR to
IWL_DEBUG_HT is the HW legacy queue is empty when driver request to move
to aggregation queue.

Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwlwifi/iwl-tx.c

@@ -1170,17 +1170,21 @@ int iwl_tx_agg_start(struct iwl_priv *priv, const u8 *ra, u16 tid, u16 *ssn)
 			__func__, ra, tid);
 
 	sta_id = iwl_find_station(priv, ra);
-	if (sta_id == IWL_INVALID_STATION)
+	if (sta_id == IWL_INVALID_STATION) {
+		IWL_ERR(priv, "Start AGG on invalid station\n");
 		return -ENXIO;
+	}
 
 	if (priv->stations[sta_id].tid[tid].agg.state != IWL_AGG_OFF) {
 		IWL_ERR(priv, "Start AGG when state is not IWL_AGG_OFF !\n");
 		return -ENXIO;
 	}
 
 	txq_id = iwl_txq_ctx_activate_free(priv);
-	if (txq_id == -1)
+	if (txq_id == -1) {
+		IWL_ERR(priv, "No free aggregation queue available\n");
 		return -ENXIO;
+	}
 
 	spin_lock_irqsave(&priv->sta_lock, flags);
 	tid_data = &priv->stations[sta_id].tid[tid];
@@ -1194,7 +1198,7 @@ int iwl_tx_agg_start(struct iwl_priv *priv, const u8 *ra, u16 tid, u16 *ssn)
 		return ret;
 
 	if (tid_data->tfds_in_queue == 0) {
-		IWL_ERR(priv, "HW queue is empty\n");
+		IWL_DEBUG_HT(priv, "HW queue is empty\n");
 		tid_data->agg.state = IWL_AGG_ON;
 		ieee80211_start_tx_ba_cb_irqsafe(priv->hw, ra, tid);
 	} else {