Allow shell to read sysfs dirs.

Bug: 26219114
Change-Id: I300899d610258704eb2d45488700eadb7a686606

shell.te

@@ -121,6 +121,7 @@ allow shell self:process ptrace;
 
 # allow shell to get battery info
 allow shell sysfs_batteryinfo:file r_file_perms;
+allow shell sysfs:dir r_dir_perms;
 
 # Allow access to ion memory allocation device.
 allow shell ion_device:chr_file rw_file_perms;