__acpi_node_get_property_reference() uses a series of if () statements for
testing the same variable. There's soon going to be one more value to be
tested.

Switch to use switch() instead.
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>