iio: imu: inv_mpu6050: simplify polling magnetometer

Do not change the sampling rate value. Let userspace decide what
is the sampling rate to use.
Read only the requested axis.

Signed-off-by: Jean-Baptiste Maneyrol <jmaneyrol@invensense.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
1 file changed