ACPI: property: Use acpi_object_type consistently in property ref parsing

The type of union acpi_object field type is acpi_object_type. Use that
instead of int.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>