s390/cio: use kobj_to_dev() API

Use kobj_to_dev() API instead of container_of().

Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: chenqiwu <chenqiwu@xiaomi.com>
Signed-off-by: chenqiwu <qiwuchen55@gmail.com>
Message-Id: <1581688293-17283-1-git-send-email-qiwuchen55@gmail.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>