iio: dac: ad5446: Don't set error code to voltage_uv

regulator_get_voltage() may return negative error code.
Add error checking to avoid setting error code to voltage_uv.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/dac/ad5446.c

@@ -226,7 +226,11 @@ static int __devinit ad5446_probe(struct device *dev, const char *name,
 		if (ret)
 			goto error_put_reg;
 
-		voltage_uv = regulator_get_voltage(reg);
+		ret = regulator_get_voltage(reg);
+		if (ret < 0)
+			goto error_disable_reg;
+
+		voltage_uv = ret;
 	}
 
 	indio_dev = iio_device_alloc(sizeof(*st));