iio: imu: fxos8700: fix MAGN sensor scale and unit

+/-1200uT is a MAGN sensor full measurement range. Magnetometer scale
is the magnetic sensitivity parameter. It is referenced as 0.1uT
according to datasheet and magnetometer channel unit is Gauss in
sysfs-bus-iio documentation. Gauss and uTesla unit conversion
relationship as follows: 0.1uT = 0.001Gs.

Set magnetometer scale and available magnetometer scale as fixed 0.001Gs.

Fixes: 84e5ddd5 ("iio: imu: Add support for the FXOS8700 IMU")
Signed-off-by: Carlos Song <carlos.song@nxp.com>
Link: https://lore.kernel.org/r/20230118074227.1665098-5-carlos.song@nxp.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/imu/fxos8700_core.c

@@ -351,7 +351,7 @@ static int fxos8700_set_scale(struct fxos8700_data *data,
 	struct device *dev = regmap_get_device(data->regmap);
 
 	if (t == FXOS8700_MAGN) {
-		dev_err(dev, "Magnetometer scale is locked at 1200uT\n");
+		dev_err(dev, "Magnetometer scale is locked at 0.001Gs\n");
 		return -EINVAL;
 	}
 
@@ -396,7 +396,7 @@ static int fxos8700_get_scale(struct fxos8700_data *data,
 	static const int scale_num = ARRAY_SIZE(fxos8700_accel_scale);
 
 	if (t == FXOS8700_MAGN) {
-		*uscale = 1200; /* Magnetometer is locked at 1200uT */
+		*uscale = 1000; /* Magnetometer is locked at 0.001Gs */
 		return 0;
 	}
 
@@ -588,7 +588,7 @@ static IIO_CONST_ATTR(in_accel_sampling_frequency_available,
 static IIO_CONST_ATTR(in_magn_sampling_frequency_available,
 		      "1.5625 6.25 12.5 50 100 200 400 800");
 static IIO_CONST_ATTR(in_accel_scale_available, "0.000244 0.000488 0.000976");
-static IIO_CONST_ATTR(in_magn_scale_available, "0.000001200");
+static IIO_CONST_ATTR(in_magn_scale_available, "0.001000");
 
 static struct attribute *fxos8700_attrs[] = {
 	&iio_const_attr_in_accel_sampling_frequency_available.dev_attr.attr,