ACPICA: Correctly support references in the union acpi_object.

This change fixes the support to allow references (namespace nodes)
to be passed as arguments to control methods via the evaluate object
interface. This is probably most useful for testing purposes, however.

Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>