ACPI: property: Return type of acpi_add_nondev_subnodes() should be bool

The value acpi_add_nondev_subnodes() returns is bool so change the return
type of the function to match that.

Fixes: 445b0eb0

 ("ACPI / property: Add support for data-only subnodes")
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>