ACPI: video: Fix missing native backlight on Chromebooks

Chromebooks don't have backlight in ACPI table, they suppose to use
native backlight in this case. Check presence of the CrOS embedded
controller ACPI device and prefer the native backlight if EC found.

Suggested-by: Hans de Goede <hdegoede@redhat.com>
Fixes: 2600bfa3

 ("ACPI: video: Add acpi_video_backlight_use_native() helper")
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/20221024141210.67784-1-dmitry.osipenko@collabora.com
Signed-off-by: Hans de Goede <hdegoede@redhat.com>