iio: light: st_uvis25: Add mod_devicetable.h and drop of_match_ptr

Enables probing via ACPI PRP0001 and removes an example that we don't
want people to cut and paste into new drivers.

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