add missing privapp-permissions

Hit : According to https://source.android.google.cn/devices/tech/config/perms-whitelist, you cuold run development/tools/privapp_permissions/privapp_permissions.py after builing the system image to find out what privapp-permissions are missing.
diff --git a/app/src/main/privapp_whitelist_org.exthmui.game.xml b/app/src/main/privapp_whitelist_org.exthmui.game.xml
index 684dfb4..8a06482 100644
--- a/app/src/main/privapp_whitelist_org.exthmui.game.xml
+++ b/app/src/main/privapp_whitelist_org.exthmui.game.xml
@@ -17,5 +17,6 @@
 <permissions>
     <privapp-permissions package="org.exthmui.game">
         <permission name="android.permission.MEDIA_CONTENT_CONTROL"/>
+        <permission name="android.permission.MODIFY_PHONE_STATE"/>
     </privapp-permissions>
 </permissions>