iio: humidity: hdc3020: switch to 16bit register defines

Switch to 16bit register defines and drop the const u8 register pairs.
By doing so we change the parameter of functions for reading and writing
to the device. Additionally create helper functions that are aware of the
new register format and apply them wherever possible.

Signed-off-by: Dimitri Fedrau <dima.fedrau@gmail.com>
Link: https://lore.kernel.org/r/20240214085350.19382-2-dima.fedrau@gmail.com


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