iio:ABI docs: Fix issue around repeated definition of out_currentY_raw

This one is challenging as both the places this appears in specific drivers
are making 'unusual' uses of what looks like a simple output current
channel.
As a side note, this was particular bit of ABI occurs in other drivers
where the use is much more straight forward e.g. dac/ad5421

This patch attempts to make a best effort of adding it to the main docs but
retaining enough information. Both of these drivers probably need
specific documents being written to describe their unusual interfaces, but
those should be in the main documentation, not under Documentation/ABI.
That is a non trivial job so left for another time.

Fixes
$ scripts/get_abi.pl validate
Warning: /sys/bus/iio/devices/iio:deviceX/out_currentY_raw is defined 2 times: ./Documentation/ABI/testing/sysfs-bus-iio-light-lm3533-als:43 ./Documentation/ABI/testing/sysfs-bus-iio-health-afe440x:38

Reported-by: Mauro Carvalho Chehab <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

Documentation/ABI/testing/sysfs-bus-iio

···
 		specified and unique if the output corresponds to a single
 		channel.
 
+What:		/sys/bus/iio/devices/iio:deviceX/out_currentY_raw
+Date:		May 2012
+KernelVersion:	3.5
+Contact:	Johan Hovold <[e-mail]>
+Description:
+		Set/get output current for channel Y. Units after application
+		of scale and offset are milliamps.
+		For some devices current channels are used to specify
+		current supplied to elements used in taking a measurement
+		of a different type. E.g. LED currents.
+
 What:		/sys/bus/iio/devices/iio:deviceX/events
 KernelVersion:	2.6.35
 Contact:	[e-mail]

Documentation/ABI/testing/sysfs-bus-iio-health-afe440x

···
 		respectively which simply helper channels containing the
 		calculated difference in the value of stage 1 - 2 and 3 - 4.
 		The values are expressed in 24-bit twos complement.
+		The LED current for the stage is controlled via
+		out_currentY_raw.
 
 What:		/sys/bus/iio/devices/iio:deviceX/in_intensityY_offset
 Date:		May 2016
···
 Description:
 		Get and set the resistance and the capacitance settings for the
 		Transimpedance Amplifier during the associated stage.
-
-What:		/sys/bus/iio/devices/iio:deviceX/out_currentY_raw
-Date:		May 2016
-KernelVersion:
-Contact:	Andrew F. Davis <[e-mail]>
-Description:
-		Get and set the LED current for the specified LED active during
-		this stage. Y is the specific stage number.

Documentation/ABI/testing/sysfs-bus-iio-light-lm3533-als

···
 		Get the current light zone (0..4) as defined by the
 		in_illuminance0_threshY_{falling,rising} thresholds.
 
-What:		/sys/bus/iio/devices/iio:deviceX/out_currentY_raw
-Date:		May 2012
-KernelVersion:	3.5
-Contact:	Johan Hovold <[e-mail]>
-Description:
-		Get output current for channel Y (0..255), that is,
-		out_currentY_currentZ_raw, where Z is the current zone.
-
 What:		/sys/bus/iio/devices/iio:deviceX/out_currentY_currentZ_raw
 Date:		May 2012
 KernelVersion:	3.5
···
 
 		These values correspond to the ALS-mapper target registers for
 		ALS-mapper Y + 1.
+
+		Note that out_currentY_raw provides the current for the
+		current zone.