Grant MediaProvider access to /mnt/media_rw

Copied access from the old mediaprovider.te to the new
mediaprovider_app.te.

Test: MediaProvider can create dirs on /mnt/media_rw/<uuid>
Bug: 151981237
Change-Id: Icdb260d2e76a05a15512a5dd00e08f8ae861dce6
diff --git a/private/mediaprovider_app.te b/private/mediaprovider_app.te
index 0b1047a..7923649 100644
--- a/private/mediaprovider_app.te
+++ b/private/mediaprovider_app.te
@@ -39,4 +39,7 @@
   FS_IOC_SETFLAGS
 };
 
+# Access external sdcards through /mnt/media_rw
+allow mediaprovider_app { mnt_media_rw_file }:dir search;
+
 allow mediaprovider_app proc_filesystems:file r_file_perms;