drm/panel-novatek-nt35510: Emit an error message if power off fails

Returning an error code from a mipi_dsi remove callback fails, this is
silently ignored. (mipi_dsi_drv_remove() propagates the return value to
device_remove() which ignores it.) So emit an error code in the driver
remove function and return 0.

Signed-off-by: Uwe Kleine-König <[e-mail]>
Reviewed-by: Sam Ravnborg <[e-mail]>
Signed-off-by: Sam Ravnborg <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/panel/panel-novatek-nt35510.c

···
 	mipi_dsi_detach(dsi);
 	/* Power off */
 	ret = nt35510_power_off(nt);
+	if (ret)
+		dev_err(&dsi->dev, "Failed to power off\n");
+
 	drm_panel_remove(&nt->panel);
 
-	return ret;
+	return 0;
 }
 
 /*