settings: add support for configurable adaptive backlight (3/4)

  adds support for kernels that use a case based adaptive backlight setting

  to enable add <bool name=config_configurable_adaptive_backlight>true</bool>   in device overlays

Change-Id: I1f1ddce34fa4fc7b2b5df81b6623d997e460cccb
make sure the configurable adaptive backlight pref only shows on supported devices

Change-Id: I1aca7576c0bdb2b25874e6c08c404024495c53be