ACPI / container: Use common hotplug code

Switch the ACPI container driver to using common device hotplug code
introduced previously.  This reduces the driver down to a trivial
definition and registration of a struct acpi_scan_handler object.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Toshi Kani <toshi.kani@hp.com>
Tested-by: Toshi Kani <toshi.kani@hp.com>