media: i2c: et8ek8: use DEVICE_ATTR_RO() helper macro

Use DEVICE_ATTR_RO() helper macro instead of DEVICE_ATTR(), which is
simpler and more readable.

Due to the name of the read function of the sysfs attribute is normalized,
there is a natural association.

Signed-off-by: Zhen Lei <[e-mail]>
Acked-by: Pavel Machek <[e-mail]>
Signed-off-by: Sakari Ailus <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/i2c/et8ek8/et8ek8_driver.c

···
  * sysfs attributes
  */
 static ssize_t
-et8ek8_priv_mem_read(struct device *dev, struct device_attribute *attr,
-		     char *buf)
+priv_mem_show(struct device *dev, struct device_attribute *attr, char *buf)
 {
 	struct v4l2_subdev *subdev = dev_get_drvdata(dev);
 	struct et8ek8_sensor *sensor = to_et8ek8_sensor(subdev);
···
 
 	return ET8EK8_PRIV_MEM_SIZE;
 }
-static DEVICE_ATTR(priv_mem, 0444, et8ek8_priv_mem_read, NULL);
+static DEVICE_ATTR_RO(priv_mem);
 
 /* --------------------------------------------------------------------------
  * V4L2 subdev core operations