iwlwifi: showing accumulative ucode statistics counters

Adding accumulative statistics counters in iwlwifi driver.
Statistics counters are reported by uCode every beacon interval; but can
be reset by uCode when needed. The accumulative statistics counters is
maintained by driver to keep track of the history of all the counters.

Update the ucode stats files in debugfs to display both latest and
accumulative counters.

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>
diff --git a/drivers/net/wireless/iwlwifi/iwl-dev.h b/drivers/net/wireless/iwlwifi/iwl-dev.h
index 6d7c235..8d087f0 100644
--- a/drivers/net/wireless/iwlwifi/iwl-dev.h
+++ b/drivers/net/wireless/iwlwifi/iwl-dev.h
@@ -1124,7 +1124,9 @@
 	struct iwl_tt_mgmt thermal_throttle;
 
 	struct iwl_notif_statistics statistics;
-	unsigned long last_statistics_time;
+#ifdef CONFIG_IWLWIFI_DEBUG
+	struct iwl_notif_statistics accum_statistics;
+#endif
 
 	/* context information */
 	u16 rates_mask;