adi:AD7606x:Add support for AD7606x family of parts

[commodo]

This change adds support for AD7605-4, AD7606-4, AD7606-6, AD7606-8, AD7606B, AD7606C-16 and AD7606C-18 parts.

All these parts are in the same family of precision ADCs.

Pull Request Description

Please replace this with a detailed description and motivation of the changes.
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If this PR contains a breaking change, list dependent PRs and try to push all related PRs at the same time.

PR Type

• Bug fix (change that fixes an issue)
• New feature (change that adds new functionality)
• Breaking change (has dependencies in other repos or will cause CI to fail)

PR Checklist

• I have performed a self-review of the changes
• I have commented my code, at least hard-to-understand parts
• I have build all projects affected by the changes in this PR
• I have tested in hardware affected projects, at the relevant boards
• I have signed off all commits from this PR
• I have updated the documentation by running /docs/source/reference_api/gen_sysobj_doc.m script locally, if applies.

[CLAassistant]

All committers have signed the CLA.