iio: hid-sensor-als: Remove hardcoding of values for enums

Remove hardcoding of values for enum CHANNEL_SCAN_INDEX_INTENSITY and
CHANNEL_SCAN_INDEX_ILLUM.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Link: https://lore.kernel.org/r/20240205185926.3030521-3-srinivas.pandruvada@linux.intel.com


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