Use kobj_to_dev() instead of open-coding it
Signed-off-by: dongjian <dongjian@yulong.com>
Link: https://lore.kernel.org/r/1615877987-32163-1-git-send-email-dj0227@163.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>