iwlwifi: add checking for the condition to reduce tx power

When bluetooth coex is active and certain condition matched,
driver need to decide should the tx power been reduce or not.
Adding the logic to manage it.

Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
diff --git a/drivers/net/wireless/iwlwifi/iwl-dev.h b/drivers/net/wireless/iwlwifi/iwl-dev.h
index f70219c..7006237 100644
--- a/drivers/net/wireless/iwlwifi/iwl-dev.h
+++ b/drivers/net/wireless/iwlwifi/iwl-dev.h
@@ -921,6 +921,7 @@
 	__le32 kill_ack_mask;
 	__le32 kill_cts_mask;
 	__le16 bt_valid;
+	bool reduced_txpower;
 	u16 bt_on_thresh;
 	u16 bt_duration;
 	u16 dynamic_frag_thresh;