spi: at91-usart: Use PTR_ERR_OR_ZERO() to simplify code

Return PTR_ERR_OR_ZERO() instead of return 0 or PTR_ERR() to
simplify code.
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
Link: https://lore.kernel.org/r/20230822124643.987079-1-ruanjinjie@huawei.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-at91-usart.c

@@ -485,10 +485,7 @@ static int at91_usart_gpio_setup(struct platform_device *pdev)
 
 	cs_gpios = devm_gpiod_get_array_optional(&pdev->dev, "cs", GPIOD_OUT_LOW);
 
-	if (IS_ERR(cs_gpios))
-		return PTR_ERR(cs_gpios);
-
-	return 0;
+	return PTR_ERR_OR_ZERO(cs_gpios);
 }
 
 static int at91_usart_spi_probe(struct platform_device *pdev)