Add context for checkin directory

Checkin apps use /data/misc_ce/<id>/checkin to backup the checkin
metadata. So users won't lose the checkin tokens when they clear
the app's storage.

One example is when GMScore is used for checkin, users may clear
GMScore data via "settings". If the device accidentally loses the
token without backup, it won't be able to checkin again until
factory reset.

The contents in checkin dir will be cleaned up when a user is removed
from the device. We also plan to add Gmscore test to ensure the dir
is cleaned up at checkin time, thus prevent other Gmscore modules
from using this storage by mistake.

Bug: 197636740
Test: boot device, check selinux label, check gmscore writes to the new dir
Change-Id: If3ff5e0fb75b4d49ce80d91b0086b58db002e4fb
diff --git a/private/file.te b/private/file.te
index 7e0bdd2..f2d3f56 100644
--- a/private/file.te
+++ b/private/file.te
@@ -30,6 +30,9 @@
 # of application data.
 type rollback_data_file, file_type, data_file_type, core_data_file_type;
 
+# /data/misc_ce/checkin for checkin apps.
+type checkin_data_file, file_type, data_file_type, core_data_file_type;
+
 # /data/gsi/ota
 type ota_image_data_file, file_type, data_file_type, core_data_file_type;