add spdx licence identifiers to remaining files

app/src/main/res/xml/prefs_screen_debug.xml

@@ -1,19 +1,9 @@
 <?xml version="1.0" encoding="utf-8"?>
-<!-- Copyright (C) 2010 The Android Open Source Project
-
-     Licensed under the Apache License, Version 2.0 (the "License");
-     you may not use this file except in compliance with the License.
-     You may obtain a copy of the License at
-
-          http://www.apache.org/licenses/LICENSE-2.0
-
-     Unless required by applicable law or agreed to in writing, software
-     distributed under the License is distributed on an "AS IS" BASIS,
-     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-     See the License for the specific language governing permissions and
-     limitations under the License.
+<!--
+    Copyright (C) 2010 The Android Open Source Project
+    modified
+    SPDX-License-Identifier: Apache-2.0 AND GPL-3.0-only
 -->
-
 <PreferenceScreen
     xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:latin="http://schemas.android.com/apk/res-auto"