video: fbdev: wm8505fb: convert platform driver to use dev_groups

Platform drivers now have the option to have the platform core create
and remove any needed sysfs attribute files.  So take advantage of that
and do not register "by hand" a sysfs file.

Cc: Tony Prisk <linux@prisktech.co.nz>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: dri-devel@lists.freedesktop.org
Cc: linux-fbdev@vger.kernel.org
Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20190731124349.4474-9-gregkh@linuxfoundation.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/video/fbdev/wm8505fb.c

@@ -176,6 +176,12 @@ static ssize_t contrast_store(struct device *dev,
 
 static DEVICE_ATTR_RW(contrast);
 
+static struct attribute *wm8505fb_attrs[] = {
+	&dev_attr_contrast.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(wm8505fb);
+
 static inline u_int chan_to_field(u_int chan, struct fb_bitfield *bf)
 {
 	chan &= 0xffff;
@@ -361,10 +367,6 @@ static int wm8505fb_probe(struct platform_device *pdev)
 		return ret;
 	}
 
-	ret = device_create_file(&pdev->dev, &dev_attr_contrast);
-	if (ret < 0)
-		fb_warn(&fbi->fb, "failed to register attributes (%d)\n", ret);
-
 	fb_info(&fbi->fb, "%s frame buffer at 0x%lx-0x%lx\n",
 		fbi->fb.fix.id, fbi->fb.fix.smem_start,
 		fbi->fb.fix.smem_start + fbi->fb.fix.smem_len - 1);
@@ -376,8 +378,6 @@ static int wm8505fb_remove(struct platform_device *pdev)
 {
 	struct wm8505fb_info *fbi = platform_get_drvdata(pdev);
 
-	device_remove_file(&pdev->dev, &dev_attr_contrast);
-
 	unregister_framebuffer(&fbi->fb);
 
 	writel(0, fbi->regbase);
@@ -399,6 +399,7 @@ static struct platform_driver wm8505fb_driver = {
 	.driver		= {
 		.name	= DRIVER_NAME,
 		.of_match_table = wmt_dt_ids,
+		.dev_groups	= wm8505fb_groups,
 	},
 };