iio: hid-sensor-als: Assign channels dynamically

Instead of assuming that every channel defined statically by
als_channels[] is present, assign dynamically based on presence of the
respective usage id in the descriptor. This will allow to register ALS
with limited channel support. Append the timestamp as the last channel.

Update available_scan_mask to specify all channels which are present.

There is no intentional function changes done.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Link: https://lore.kernel.org/r/20240205185926.3030521-2-srinivas.pandruvada@linux.intel.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>