iio: resistance: Document that resistance can be output

Signed-off-by: NPeter Rosin <peda@axentia.se>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>

Documentation/ABI/testing/sysfs-bus-iio

@@ -1474,6 +1474,8 @@ Description:
 
 What:		/sys/bus/iio/devices/iio:deviceX/in_resistance_raw
 What:		/sys/bus/iio/devices/iio:deviceX/in_resistanceX_raw
+What:		/sys/bus/iio/devices/iio:deviceX/out_resistance_raw
+What:		/sys/bus/iio/devices/iio:deviceX/out_resistanceX_raw
 KernelVersion:	4.3
 Contact:	linux-iio@vger.kernel.org
 Description: