iwlwifi: "tx power per chain" are part of ucode_tx_stats

Move "tx power per chain" into ucode_tx_stats, it is debugging
information provided by uCode as part of statistics notification.

The "tx power per chain" parameters are optional parameters which only
supported by 6000 series device today; those are reserved fields for all
the other devices.

Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
diff --git a/drivers/net/wireless/iwlwifi/iwl-commands.h b/drivers/net/wireless/iwlwifi/iwl-commands.h
index 449d41f..9aab020 100644
--- a/drivers/net/wireless/iwlwifi/iwl-commands.h
+++ b/drivers/net/wireless/iwlwifi/iwl-commands.h
@@ -3127,6 +3127,11 @@
 	__le32 cts_timeout_collision;
 	__le32 ack_or_ba_timeout_collision;
 	struct statistics_tx_non_phy_agg agg;
+	/*
+	 * "tx_power" are optional parameters provided by uCode,
+	 * 6000 series is the only device provide the information,
+	 * Those are reserved fields for all the other devices
+	 */
 	struct statistics_tx_power tx_power;
 	__le32 reserved1;
 } __attribute__ ((packed));