iio: light: hid-sensor-als: Add duplicate IIO_LIGHT channel

There is one light sensor type defined in the sensor hub specification,
which has one Illuminance field. It doesn't distinguish between ambient
light sensor or color sensor. Currently it is presented as IIO_INTENSITY
channel. There are some user spaces specifically looking for IIO_LIGHT
channel.
To satisfy such user spaces this change also add a duplicate IIO_LIGHT
channel. The units of measurement of Illuminance field is Lux, so it is
still compatible to IIO ABI.

Signed-off-by: Kweh, Hock Leong <hock.leong.kweh@intel.com>
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>