iio: light: vl6180: add include of mod_devicetable.h and drop of_match_ptr

Enables probing via ACPI PRP0001 route and removes an example of
an approach we no longer want people to copy.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Alexandru Ardelean <alexandru.ardelean@analog.com>