iio: add documentation for current attribute

Add documentation for input current raw sysfs attribute.

Signed-off-by: Jacob Pan <[email protected]>
Signed-off-by: Jonathan Cameron <[email protected]>
diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
index d760b02..1ac9ac2 100644
--- a/Documentation/ABI/testing/sysfs-bus-iio
+++ b/Documentation/ABI/testing/sysfs-bus-iio
@@ -1028,3 +1028,12 @@
 Description:
 		Raw value of rotation from true/magnetic north measured with
 		or without compensation from tilt sensors.
+
+What:		/sys/bus/iio/devices/iio:deviceX/in_currentX_raw
+KernelVersion:	3.18
+Contact:	[email protected]
+Description:
+		Raw current measurement from channel X. Units are in milliamps
+		after application of scale and offset. If no offset or scale is
+		present, output should be considered as processed with the
+		unit in milliamps.