Fix output data formatting and limited SR

[darshiltrivedi]

Description

While addition of new device to the ad463x family, ad4030(single channel version) particularly , due to changes in C drivers updates were required to python API like removal of sampling_rate_available attribute.
Addition of Continuous sampling example as it was popular customer request.

Fixes # (issue)
Previous version did bit-masking and sign solely based on number of channels but it has to be fixed as other members of ad463x family it might vary.
Sampling rate can be anything from 0 to max value now.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• This change requires a documentation update

How has this been tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• Test A
• Test B

Test Configuration:

• Hardware:
• OS:

Documentation

If this is a new feature or example please mention or link any documentation. All new hardware interface classes require documentation.

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

[darshiltrivedi]

I was wondering if I need to update anything on my end for this PR?

[tfcollins]

I was wondering if the new buffer API that was added could handle these type conversion automatically for you. As long as the format is described correctly in the IIO channel it should provide the correct output.

This was added with this commit if you want to just rebase on master: 294d9cf

[darshiltrivedi]

I moved out of my rotation from PCT team and no longer have access to the boards. I could try to rebase it and make the changes but not sure it will work since I could not test them on actual board.

[darshiltrivedi]

Hello Travis,
Like I mentioned, I do not have a hardware setup and worried I would break existing functionality in making changes. Can this be merged without it? If, not I can request the team to lend me the hardware, so I could confirm it.

[tfcollins]

We really need someone with hardware to valid