iio: adc: ad9467: support digital interface calibration

To make sure that we have the best timings on the serial data interface
we should calibrate it. This means going through the device supported
values and see for which ones we get a successful result. To do that, we
use a prbs test pattern both in the IIO backend and in the frontend
devices. Then for each of the test points we see if there are any
errors. Note that the backend is responsible to look for those errors.

As calibrating the interface also requires that the data format is disabled
(the one thing being done in ad9467_setup()), ad9467_setup() was removed
and configuring the data fomat is now part of the calibration process.

Signed-off-by: Nuno Sa <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20240426-ad9467-new-features-v2-7-6361fc3ba1cc@analog.com


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