ACPI: register ACPI Video LCD as generic thermal cooling device

Register ACPI video device as thermal cooling devices as they may be listed
in _TZD method and the backlight control can be used for throttling.

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Thomas Sujith <sujith.thomas@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>