iio: adc: qcom-pm8xxx-xoadc: 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.

BTW, change the return value from 'ENXIO' to 'ENODEV',
perfer ENODEV which means no such device.
Signed-off-by: Cai Huoqing <caihuoqing@baidu.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20211008092858.495-7-caihuoqing@baidu.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/qcom-pm8xxx-xoadc.c

@@ -910,16 +910,15 @@ static int pm8xxx_xoadc_probe(struct platform_device *pdev)
 	map = dev_get_regmap(dev->parent, NULL);
 	if (!map) {
 		dev_err(dev, "parent regmap unavailable.\n");
-		return -ENXIO;
+		return -ENODEV;
 	}
 	adc->map = map;
 
 	/* Bring up regulator */
 	adc->vref = devm_regulator_get(dev, "xoadc-ref");
-	if (IS_ERR(adc->vref)) {
-		dev_err(dev, "failed to get XOADC VREF regulator\n");
-		return PTR_ERR(adc->vref);
-	}
+	if (IS_ERR(adc->vref))
+		return dev_err_probe(dev, PTR_ERR(adc->vref),
+				     "failed to get XOADC VREF regulator\n");
 	ret = regulator_enable(adc->vref);
 	if (ret) {
 		dev_err(dev, "failed to enable XOADC VREF regulator\n");