recovery allows to read mapper_block_device:dir.

Bug: 152177002
Test: none
Change-Id: I82683433c24764cbe449c140b7805f4ed0b4ecca
(cherry picked from commit 486e12b91086eecd89f6d56769352b45424b69d0)
diff --git a/vendor/google/recovery.te b/vendor/google/recovery.te
index 7e7925c..7e711ea 100644
--- a/vendor/google/recovery.te
+++ b/vendor/google/recovery.te
@@ -2,4 +2,5 @@
  allow recovery citadel_device:chr_file rw_file_perms;
  allow recovery sg_device:chr_file rw_file_perms;
  allow recovery sysfs_scsi_devices_0000:dir r_dir_perms;
+ allow recovery mapper_block_device:dir r_dir_perms;
 ')