Remove hal_light from system_server domain

HAL clients should not be annotated with hal_x and haldomain. This may
grant them too much access. Instead, the policy needed for using
in-process HALs should be directly embedded into the client's domain
rules.

Test: Boot sailfish, adjust screen brightness from the system UI, no
      SELinux denials for system_server to do with sysfs_leds.
Bug: 34715716

Change-Id: Iccb4224d770583e3c38930e8562723d57d283077