iio: adc: twl4030: Fix an error handling path in 'twl4030_madc_probe()'

If 'devm_regulator_get()' fails, we should go through the existing error
handling path instead of returning directly, as done is all the other
error handling paths in this function.

Fixes: 7cc97d77ee8a ("iio: adc: twl4030: Fix ADC[3:6] readings")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/twl4030-madc.c

@@ -887,8 +887,10 @@ static int twl4030_madc_probe(struct platform_device *pdev)
 
 	/* Enable 3v1 bias regulator for MADC[3:6] */
 	madc->usb3v1 = devm_regulator_get(madc->dev, "vusb3v1");
-	if (IS_ERR(madc->usb3v1))
-		return -ENODEV;
+	if (IS_ERR(madc->usb3v1)) {
+		ret = -ENODEV;
+		goto err_i2c;
+	}
 
 	ret = regulator_enable(madc->usb3v1);
 	if (ret)