drm: rcar-du: error message is not needed for EPROBE_DEFER

EPROBE_DEFER is not error, thus, error message on kernel log on this
case is confusable. Print it only error cases

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>

drivers/gpu/drm/rcar-du/rcar_du_drv.c

@@ -345,7 +345,9 @@ static int rcar_du_probe(struct platform_device *pdev)
 	/* DRM/KMS objects */
 	ret = rcar_du_modeset_init(rcdu);
 	if (ret < 0) {
-		dev_err(&pdev->dev, "failed to initialize DRM/KMS (%d)\n", ret);
+		if (ret != -EPROBE_DEFER)
+			dev_err(&pdev->dev,
+				"failed to initialize DRM/KMS (%d)\n", ret);
 		goto error;
 	}