ACPI / Documentation: update ACPI customize method feature docs

Reviewed-by: Changzhong Li <changzhong.li@intel.com>
Reviewed-by: Rui Zhang <rui.zhang@intel.com>
Signed-off-by: Erik Schmauss <erik.schmauss@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>