private: hal_widevine_system: support private storage

- mediadrm_system_data_file file type
- make  it private to hal_widevine_system

Bug: 371777025
Test: lunch qemu_trusty_arm64-trunk_staging-userdebug
Change-Id: I5bd28eb4f2eaa44bb0b5a934b7919d2b959ec098
diff --git a/private/app.te b/private/app.te
index a32cdb2..3219fbe 100644
--- a/private/app.te
+++ b/private/app.te
@@ -609,6 +609,8 @@
     { create write setattr relabelfrom relabelto append unlink link rename };
 
 # Write to various other parts of /data.
+neverallow appdomain mediadrm_system_data_file:dir_file_class_set
+    { create write setattr relabelfrom relabelto append unlink link rename };
 neverallow appdomain drm_data_file:dir_file_class_set
     { create write setattr relabelfrom relabelto append unlink link rename };
 neverallow { appdomain -platform_app }