video: fbdev: mb862xx: use DEVICE_ATTR_RO macro

Use DEVICE_ATTR_RO helper instead of plain DEVICE_ATTR, which makes the
code a bit shorter and easier to read.
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210601090852.10531-1-thunder.leizhen@huawei.com

drivers/video/fbdev/mb862xx/mb862xxfbdrv.c

@@ -542,8 +542,8 @@ static int mb862xxfb_init_fbinfo(struct fb_info *fbi)
 /*
  * show some display controller and cursor registers
  */
-static ssize_t mb862xxfb_show_dispregs(struct device *dev,
-				       struct device_attribute *attr, char *buf)
+static ssize_t dispregs_show(struct device *dev,
+			     struct device_attribute *attr, char *buf)
 {
 	struct fb_info *fbi = dev_get_drvdata(dev);
 	struct mb862xxfb_par *par = fbi->par;
@@ -577,7 +577,7 @@ static ssize_t mb862xxfb_show_dispregs(struct device *dev,
 	return ptr - buf;
 }
 
-static DEVICE_ATTR(dispregs, 0444, mb862xxfb_show_dispregs, NULL);
+static DEVICE_ATTR_RO(dispregs);
 
 static irqreturn_t mb862xx_intr(int irq, void *dev_id)
 {