ad469x: make compatible with latest driver

[threexc]

adi/ad469x.py:

• make device setup logic in more similar to other recent part submissions (e.g. ad7944)
• add exception check for self._ctrl
• add sampling frequency, sampling_frequency available properties to channel (assumes ad4695 driver using SPI offload for performance)
• Update docstrings

test/test_ad469x.py:

• update to target channels voltage0 and voltage1, specify buffer size

general:

• run pre-commit for formatting and layout checks

Description

Update the existing ad469x logic to support the latest upstream driver, now that it has been reworked and will incorporate SPI offload functionality for performance purposes.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How has this been tested?

Ran the test script against the configuration below.

Test Configuration:

• Hardware: Zedboard with EVAL-AD4696FMCZ board
• OS: Kuiper Linux with custom kernel featuring ad4695 driver and SPI offload functionality

Documentation

No new docs added, but strings in class were updated a bit

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have signed off all commits and they contain "Signed-off by: "
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules