Use kobj_to_dev() instead of open-coding it.
Signed-off-by: Minghao Chi <chi.minghao@zte.com.cn>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20220511021638.1488650-1-chi.minghao@zte.com.cnSigned-off-by: Hans de Goede <hdegoede@redhat.com>