iio: dac: mcp4922: Make use of the helper function dev_err_probe()

When possible use dev_err_probe help to properly deal with the
PROBE_DEFER error, the benefit is that DEFER issue will be logged
in the devices_deferred debugfs file.
Using dev_err_probe() can reduce code size, and the error value
gets printed.
Signed-off-by: Cai Huoqing <caihuoqing@baidu.com>
Link: https://lore.kernel.org/r/20210928013902.1341-6-caihuoqing@baidu.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/dac/mcp4922.c

@@ -130,10 +130,9 @@ static int mcp4922_probe(struct spi_device *spi)
 	state = iio_priv(indio_dev);
 	state->spi = spi;
 	state->vref_reg = devm_regulator_get(&spi->dev, "vref");
-	if (IS_ERR(state->vref_reg)) {
-		dev_err(&spi->dev, "Vref regulator not specified\n");
-		return PTR_ERR(state->vref_reg);
-	}
+	if (IS_ERR(state->vref_reg))
+		return dev_err_probe(&spi->dev, PTR_ERR(state->vref_reg),
+				     "Vref regulator not specified\n");
 
 	ret = regulator_enable(state->vref_reg);
 	if (ret) {