allow toolbox block_device:dir search

needed to get to the swap device.

Addresses the following denial:

  avc:  denied  { search } for  pid=149 comm="mkswap" name="block" dev="tmpfs" ino=9947 scontext=u:r:toolbox:s0 tcontext=u:object_r:block_device:s0 tclass=dir permissive=0

Change-Id: I0c897540f1c7950738622a013121a050a1f32b2f

toolbox.te

@@ -18,6 +18,7 @@ allow toolbox devpts:chr_file { read write getattr ioctl };
 # Read/write block devices used for swap partitions.
 # Assign swap_block_device type any such partition in your
 # device/<vendor>/<product>/sepolicy/file_contexts file.
+allow toolbox block_device:dir search;
 allow toolbox swap_block_device:blk_file rw_file_perms;
 
 # Only allow entry from init via the toolbox binary.