cm: sepolicy: Allow system_server dir read access

Change-Id: Ia6fc26781c1cb576c2feee3e941d7206e7878bb5
diff --git a/sepolicy/system_server.te b/sepolicy/system_server.te
index 6aaf50c..39ee935 100644
--- a/sepolicy/system_server.te
+++ b/sepolicy/system_server.te
@@ -7,3 +7,5 @@
 allow system_server persist_property_file:file { create_file_perms unlink };
 
 allow system_server storage_stub_file:dir { getattr };
+
+allow system_server media_rw_data_file:dir r_dir_perms;