Add rules for vfat for sdcardfs

This adds parellel rules to the ones added for media_rw_data_file
to allow apps to access vfat under sdcardfs. This should be reverted
if sdcardfs is modified to alter the secontext it used for access to
the lower filesystem

Change-Id: Idb123206ed2fac3ead88b0c1ed0b66952597ac65
Bug: 62584229
Test: Run android.appsecurity.cts.ExternalStorageHostTest with
      an external card formated as vfat
Signed-off-by: Daniel Rosenberg <drosen@google.com>

private/app.te

@@ -225,8 +225,8 @@ allow { appdomain -isolated_app -ephemeral_app } sdcardfs:dir create_dir_perms;
 allow { appdomain -isolated_app -ephemeral_app } sdcardfs:file create_file_perms;
 # This should be removed if sdcardfs is modified to alter the secontext for its
 # accesses to the underlying FS.
-allow { appdomain -isolated_app -ephemeral_app } media_rw_data_file:dir create_dir_perms;
-allow { appdomain -isolated_app -ephemeral_app } media_rw_data_file:file create_file_perms;
+allow { appdomain -isolated_app -ephemeral_app } { media_rw_data_file vfat }:dir create_dir_perms;
+allow { appdomain -isolated_app -ephemeral_app } { media_rw_data_file vfat }:file create_file_perms;
 
 # Access OBBs (vfat images) mounted by vold (b/17633509)
 # File write access allowed for FDs returned through Storage Access Framework