drm: Use PTR_ERR_OR_ZERO in drm_fb_cma_fbdev_init()

Use PTR_ERR_OR_ZERO rather than if(IS_ERR(...)) + PTR_ERR

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/1539176563-144779-1-git-send-email-yuehaibing@huawei.com

drivers/gpu/drm/drm_fb_cma_helper.c

@@ -124,10 +124,7 @@ int drm_fb_cma_fbdev_init(struct drm_device *dev, unsigned int preferred_bpp,
 
 	/* dev->fb_helper will indirectly point to fbdev_cma after this call */
 	fbdev_cma = drm_fbdev_cma_init(dev, preferred_bpp, max_conn_count);
-	if (IS_ERR(fbdev_cma))
-		return PTR_ERR(fbdev_cma);
-
-	return 0;
+	return PTR_ERR_OR_ZERO(fbdev_cma);
 }
 EXPORT_SYMBOL_GPL(drm_fb_cma_fbdev_init);