Documentation: ABI: add specific icm42600 documentation

Hardware offset available as calibscale sysfs attributes are real
physical values exprimed in SI units.

calibscale_available sysfs attributes represents the range of
acceptable values.
Signed-off-by: NJean-Baptiste Maneyrol <jmaneyrol@invensense.com>
Signed-off-by: NJonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/ABI/testing/sysfs-bus-iio-icm42600

+What:		/sys/bus/iio/devices/iio:deviceX/in_accel_x_calibbias
+What:		/sys/bus/iio/devices/iio:deviceX/in_accel_y_calibbias
+What:		/sys/bus/iio/devices/iio:deviceX/in_accel_z_calibbias
+What:		/sys/bus/iio/devices/iio:deviceX/in_anglvel_x_calibbias
+What:		/sys/bus/iio/devices/iio:deviceX/in_anglvel_y_calibbias
+What:		/sys/bus/iio/devices/iio:deviceX/in_anglvel_z_calibbias
+KernelVersion:  5.8
+Contact:        linux-iio@vger.kernel.org
+Description:
+		Hardware applied calibration offset (assumed to fix production
+		inaccuracies). Values represent a real physical offset expressed
+		in SI units (m/s^2 for accelerometer and rad/s for gyroscope).
+
+What:		/sys/bus/iio/devices/iio:deviceX/in_accel_calibbias_available
+What:		/sys/bus/iio/devices/iio:deviceX/in_anglvel_calibbias_available
+KernelVersion:  5.8
+Contact:        linux-iio@vger.kernel.org
+Description:
+		Range of available values for hardware offset. Values in SI
+		units (m/s^2 for accelerometer and rad/s for gyroscope).