sepolicy: Add permissions for LCD brightness control

 Add rule to provide permission for the hal_light_default context
 to read and write the sysfs node that corresponds to LCD
 brightness.
 Add rules to provide permission for the init context to change
 attributes of files under the sysfs and sysfs_graphics contexts.

Change-Id: If8e71b0d6baa174c80369a808d427151f178c5d6
2 files changed