Allow access to the metadata partition for metadata encryption.

Bug: 63927601
Test: Enable metadata encryption in fstab on Taimen, check boot success.
Change-Id: Id425c47d48f413d6ea44ed170835a52d0af39f9f
diff --git a/private/fsck.te b/private/fsck.te
index 3a36329..f8e09b6 100644
--- a/private/fsck.te
+++ b/private/fsck.te
@@ -1,3 +1,5 @@
 typeattribute fsck coredomain;
 
 init_daemon_domain(fsck)
+
+allow fsck metadata_block_device:blk_file rw_file_perms;