iio: dac: ad3552r: add model data structure

iio: dac: ad3552r: add model data structure

Add a "model data" structure to keep useful hardware-related
information as from datasheet, avoiding id-based conditional
choices later on.

Removed id-based checks and filled model-specific structures
with device specific features, In particular, num_hw_channels
is introduced to keep the number of hardware implemented
channels, since 1-channel versions of the DACs are added
in this same patchset.

Signed-off-by: Angelo Dureghello <adureghello@baylibre.com>
Reviewed-by: Nuno Sa <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20240522150141.1776196-4-adureghello@baylibre.org
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>