drm/panel: otm8009a: Drop unnessary backlight_device_unregister()

It's not necessary to unregister backlight device which
registered with devm_backlight_device_register().

Fixes: 12a6cbd4 ("drm/panel: otm8009a: Use new backlight API")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200618134650.44311-1-weiyongjun1@huawei.com

drivers/gpu/drm/panel/panel-orisetech-otm8009a.c

@@ -479,7 +479,6 @@ static int otm8009a_probe(struct mipi_dsi_device *dsi)
 	if (ret < 0) {
 		dev_err(dev, "mipi_dsi_attach failed. Is host ready?\n");
 		drm_panel_remove(&ctx->panel);
-		backlight_device_unregister(ctx->bl_dev);
 		return ret;
 	}