iio: light: veml6030: extend regmap to support regfields

Add support for regfields as well to simplify register operations,
taking into account the different fields for the veml6030/veml7700 and
veml6035.

Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Link: https://patch.msgid.link/20250119-veml6030-scale-v2-1-6bfc4062a371@gmail.com


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