iwlagn: Add support for bluetooth statistics notification

WiFi/BT combo devices has different statistics notification
structure, adding the support here to make sure the structure
align correctly.

Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
diff --git a/drivers/net/wireless/iwlwifi/iwl-commands.h b/drivers/net/wireless/iwlwifi/iwl-commands.h
index 4be9063..04b2e29 100644
--- a/drivers/net/wireless/iwlwifi/iwl-commands.h
+++ b/drivers/net/wireless/iwlwifi/iwl-commands.h
@@ -3988,6 +3988,7 @@
 		struct iwl_sleep_notification sleep_notif;
 		struct iwl_spectrum_resp spectrum;
 		struct iwl_notif_statistics stats;
+		struct iwl_bt_notif_statistics stats_bt;
 		struct iwl_compressed_ba_resp compressed_ba;
 		struct iwl_missed_beacon_notif missed_beacon;
 		struct iwl_coex_medium_notification coex_medium_notif;