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 <mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/20210117153816.696693-5-jic23@kernel.org

iio: cleanup sysfs-bus-iio-light-lm3533-als

Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>
Acked-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

iio: add LM3533 ambient-light-sensor driver

Add sub-driver for the ambient-light-sensor interface on National
Semiconductor / TI LM3533 lighting power chips.

The sensor interface can be used to control the LEDs and backlights of
the chip through defining five light zones and three sets of
corresponding output-current values.

The driver provides raw and mean adc readings along with the current
light zone through sysfs. A threshold event can be generated on zone
changes. The ALS-control output values can be set per zone for the three
current output channels.

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Acked-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>