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>
diff --git a/drivers/net/wireless/iwlwifi/iwl-debug.h b/drivers/net/wireless/iwlwifi/iwl-debug.h
index 96c92ea..25a0e73 100644
--- a/drivers/net/wireless/iwlwifi/iwl-debug.h
+++ b/drivers/net/wireless/iwlwifi/iwl-debug.h
@@ -107,6 +107,7 @@
 		struct dentry *file_chain_noise;
 		struct dentry *file_tx_power;
 		struct dentry *file_power_save_status;
+		struct dentry *file_clear_statistics;
 	} dbgfs_debug_files;
 	u32 sram_offset;
 	u32 sram_len;