ACPI / scan: always register container scan handler

Prevent platform devices from being created for ACPI containers
if CONFIG_ACPI_CONTAINER is unset by compiling out the container
scan handler's callbacks only in that case and still compiling
its device ID list in and registering the scan handler in either
case.

This change is based on a prototype from Zhang Rui.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>