iwlwifi: update reply_statistics_cmd with 'clear' parameter

When issue REPLY_STATISTICS_CMD to uCode, two possible flag
can be set in the configuration flags

bit 0: Clear statistics
       0: Do not clear Statistics counters
       1: Clear to zero Statistics counters

Allow "clear" parameter to be set from the caller.

Add debugfs file to clear the statistics counters to help monitor and
debug the uCode behavior.

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-power.c

@@ -506,7 +506,7 @@ static void iwl_prepare_ct_kill_task(struct iwl_priv *priv)
 {
 	IWL_DEBUG_POWER(priv, "Prepare to enter IWL_TI_CT_KILL\n");
 	/* make request to retrieve statistics information */
-	iwl_send_statistics_request(priv, 0);
+	iwl_send_statistics_request(priv, CMD_SYNC, false);
 	/* Reschedule the ct_kill wait timer */
 	mod_timer(&priv->thermal_throttle.ct_kill_waiting_tm,
 		 jiffies + msecs_to_jiffies(CT_KILL_WAITING_DURATION));