service: implement HAL callback for response confirmation

Change-Id: Iec1c33574cef49053cf1f8eb3835b20047cb96eb
diff --git a/service/hal/bluetooth_gatt_interface.h b/service/hal/bluetooth_gatt_interface.h
index 99c6f6c..f8bdfdc 100644
--- a/service/hal/bluetooth_gatt_interface.h
+++ b/service/hal/bluetooth_gatt_interface.h
@@ -177,6 +177,11 @@
         int conn_id, int trans_id,
         const bt_bdaddr_t& bda, int exec_write);
 
+    virtual void ResponseConfirmationCallback(
+        BluetoothGattInterface* gatt_iface,
+        int status,
+        int handle);
+
     virtual void IndicationSentCallback(
         BluetoothGattInterface* gatt_iface, int conn_id, int status);