Allow apps to read keychain_data_file links

Bug: 28746284
Change-Id: I59aa235ecba05e22aaa531e387a77f47267ac9ae
diff --git a/app.te b/app.te
index 27e6055..21fdc8a 100644
--- a/app.te
+++ b/app.te
@@ -75,8 +75,7 @@
 allow appdomain mnt_expand_file:dir r_dir_perms;
 
 # Keychain and user-trusted credentials
-allow appdomain keychain_data_file:dir r_dir_perms;
-allow appdomain keychain_data_file:file r_file_perms;
+r_dir_file(appdomain, keychain_data_file)
 allow appdomain misc_user_data_file:dir r_dir_perms;
 allow appdomain misc_user_data_file:file r_file_perms;