allow vold_prepare_subdirs to create storaged directories

Test: Boot device, observe logs
Bug: 63740245
Change-Id: I1068304b12ea90736b7927b7368ba1a213d2fbae
diff --git a/private/vold_prepare_subdirs.te b/private/vold_prepare_subdirs.te
index c2146f9..7360e58 100644
--- a/private/vold_prepare_subdirs.te
+++ b/private/vold_prepare_subdirs.te
@@ -1 +1,3 @@
 domain_auto_trans(vold, vold_prepare_subdirs_exec, vold_prepare_subdirs)
+
+allow vold_prepare_subdirs storaged_data_file:dir create_dir_perms;