iwlagn: change the logging level for aggregation enable check

Aggregation will not enable if the traffic is lower than the threshold,
this is not an error condition, so change the logging level.
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwlwifi/iwl-agn-rs.c

@@ -426,7 +426,7 @@ static int rs_tl_turn_on_agg_for_tid(struct iwl_priv *priv,
 			ieee80211_stop_tx_ba_session(sta, tid);
 		}
 	} else {
-		IWL_ERR(priv, "Aggregation not enabled for tid %d "
+		IWL_DEBUG_HT(priv, "Aggregation not enabled for tid %d "
 			"because load = %u\n", tid, load);
 	}
 	return ret;