iio: imu: fxos8700: fix map label of channel type to MAGN sensor

iio: imu: fxos8700: fix map label of channel type to MAGN sensor

FXOS8700 is an IMU sensor with ACCEL sensor and MAGN sensor.
Sensor type is indexed by corresponding channel type in a switch.
IIO_ANGL_VEL channel type mapped to MAGN sensor has caused confusion.

Fix the mapping label of "IIO_MAGN" channel type instead of
"IIO_ANGL_VEL" channel type to MAGN sensor.

Fixes: 84e5ddd5c46e ("iio: imu: Add support for the FXOS8700 IMU")
Signed-off-by: Carlos Song <carlos.song@nxp.com>
Link: https://lore.kernel.org/r/20221208071911.2405922-2-carlos.song@nxp.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>