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>

drivers/s390/cio/chp.c

@@ -135,7 +135,7 @@ static ssize_t chp_measurement_chars_read(struct file *filp,
 	struct channel_path *chp;
 	struct device *device;
 
-	device = container_of(kobj, struct device, kobj);
+	device = kobj_to_dev(kobj);
 	chp = to_channelpath(device);
 	if (chp->cmg == -1)
 		return 0;
@@ -184,7 +184,7 @@ static ssize_t chp_measurement_read(struct file *filp, struct kobject *kobj,
 	struct device *device;
 	unsigned int size;
 
-	device = container_of(kobj, struct device, kobj);
+	device = kobj_to_dev(kobj);
 	chp = to_channelpath(device);
 	css = to_css(chp->dev.parent);