Set product_specific:true for privapp_whitelist

According to https://source.android.google.cn/devices/tech/config/perms-whitelist , the privapp-permissions.xml file can only grant or deny permissions for privileged apps on the same partition. Set this to put privapp_whitelist_org.exthmui.game.xml to the same partition which contains GamingMode app and grant permissions for this app correctly.
diff --git a/app/src/main/Android.bp b/app/src/main/Android.bp
index fb51116..4c9ec57 100644
--- a/app/src/main/Android.bp
+++ b/app/src/main/Android.bp
@@ -26,7 +26,7 @@
 
 prebuilt_etc {
     name: "privapp_whitelist_org.exthmui.game.xml",
-
+    product_specific: true,
     src: "privapp_whitelist_org.exthmui.game.xml",
     sub_dir: "permissions",