hal_light: add permission to sys/class/leds.

/sys/class/leds is the standard location for linux files dealing with
leds, however the exact contents of this directory is non-standard
(hence the need for a hal).

Bug: 32022100
Test: compiles and works for the subset of common files
Change-Id: I7571d7267d5ed531c4cf95599d5f2acc22287ef4

private/file_contexts

@@ -419,6 +419,7 @@
 #############################
 # sysfs files
 #
+/sys/class/leds(/.*)?                        u:object_r:sysfs_leds:s0
 /sys/devices/platform/nfc-power/nfc_power -- u:object_r:sysfs_nfc_power_writable:s0
 /sys/devices/system/cpu(/.*)?    u:object_r:sysfs_devices_system_cpu:s0
 /sys/devices/virtual/block/zram\d+(/.*)?     u:object_r:sysfs_zram:s0

public/file.te

@@ -32,6 +32,7 @@ type sysfs, fs_type, sysfs_type, mlstrustedobject;
 type sysfs_uio, sysfs_type, fs_type;
 type sysfs_batteryinfo, fs_type, sysfs_type;
 type sysfs_bluetooth_writable, fs_type, sysfs_type, mlstrustedobject;
+type sysfs_leds, fs_type, sysfs_type;
 type sysfs_hwrandom, fs_type, sysfs_type;
 type sysfs_nfc_power_writable, fs_type, sysfs_type, mlstrustedobject;
 type sysfs_wake_lock, fs_type, sysfs_type;

public/hal_light.te

 # call into system_server process (callbacks)
 binder_call(hal_light, system_server)
+
+allow hal_light sysfs_leds:lnk_file read;
+allow hal_light sysfs_leds:file rw_file_perms;
+allow hal_light sysfs_leds:dir r_dir_perms;