media: bttv: 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.

Link: https://lore.kernel.org/linux-media/[e-mail]

Signed-off-by: Zhen Lei <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/pci/bt8xx/bttv-driver.c

···
 /* ----------------------------------------------------------------------- */
 /* sysfs                                                                   */
 
-static ssize_t show_card(struct device *cd,
+static ssize_t card_show(struct device *cd,
 			 struct device_attribute *attr, char *buf)
 {
 	struct video_device *vfd = to_video_device(cd);
 	struct bttv *btv = video_get_drvdata(vfd);
 	return sprintf(buf, "%d\n", btv ? btv->c.type : UNSET);
 }
-static DEVICE_ATTR(card, S_IRUGO, show_card, NULL);
+static DEVICE_ATTR_RO(card);
 
 /* ----------------------------------------------------------------------- */
 /* dvb auto-load setup                                                     */