sepolicy: Allow vold to `getattr` on mkfs_exec

* Fixes denial while trying to format external
  SDcard as adopted storage.

Change-Id: I244ec9b5886888e1cbe488c671b9862b653f73a9
diff --git a/sepolicy/vold.te b/sepolicy/vold.te
index 14b9063..63e72d7 100644
--- a/sepolicy/vold.te
+++ b/sepolicy/vold.te
@@ -20,4 +20,4 @@
 # External storage
 allow vold storage_stub_file:dir { rw_file_perms search add_name };
 allow vold mnt_media_rw_stub_file:dir r_dir_perms;
-allow vold mkfs_exec:file { execute read open execute_no_trans };
+allow vold mkfs_exec:file { execute read open getattr execute_no_trans };