hwmon: iio: Use iio_read_channel_processed_scale for IIO_POWER

Instead of rescaling power channels after the fact, use the dedicated
scaling API. This should reduce any inaccuracies resulting from the
scaling.
Signed-off-by: Sean Anderson <sean.anderson@linux.dev>
Link: https://lore.kernel.org/r/20240620212005.821805-1-sean.anderson@linux.devSigned-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/iio_hwmon.c

@@ -49,16 +49,17 @@ static ssize_t iio_hwmon_read_val(struct device *dev,
 	struct iio_channel *chan = &state->channels[sattr->index];
 	enum iio_chan_type type;
 
-	ret = iio_read_channel_processed(chan, &result);
-	if (ret < 0)
-		return ret;
-
 	ret = iio_get_channel_type(chan, &type);
 	if (ret < 0)
 		return ret;
 
 	if (type == IIO_POWER)
-		result *= 1000; /* mili-Watts to micro-Watts conversion */
+		/* mili-Watts to micro-Watts conversion */
+		ret = iio_read_channel_processed_scale(chan, &result, 1000);
+	else
+		ret = iio_read_channel_processed(chan, &result);
+	if (ret < 0)
+		return ret;
 
 	return sprintf(buf, "%d\n", result);
 }