iio: frequency: ad9172: implement sysref oneshot sequence

[vai-tomme]

PR Description

Support for performing oneshot sequence as laid out in section "jesd204b serial data interface" and sync procedure of datasheet rev C [1] for device. In addition to the already implemented sysref_enable step, the other steps are also required for a sync to take place.

Feature is here implemented for subclass 1 operation with jesd-fsm enabled.

[1] https://www.analog.com/media/en/technical-documentation/data-sheets/ad9171.pdf

PR Type

• Bug fix (a change that fixes an issue)
• New feature (a change that adds new functionality)
• Breaking change (a change that affects other repos or cause CIs to fail)

PR Checklist

• I have conducted a self-review of my own code changes
• I have tested the changes on the relevant hardware
• I have updated the documentation outside this repo accordingly (if there is the case)

[gastmaier]

Hi @vai-tomme, thank you for the contribution! Please ignore the modpost error, was fixed on #2920 (1)!
But please go in the Files changed tab and apply the CI commented suggestion for your touched lines.
Minor kernel style stuff, using u* instead of uint*_t, direct null check if (!var)

(1) a cleaner run can be then created by either closing and opening the pr, or pushing a commit, to update the base branch head.

[vai-tomme]

Hi @gastmaier, thanks! I updated one occurance of uint8 to u8, but I kept the h == NULL style since that is the style used througout the file for that particular driver.
Please let me know if you still prefer me to update the null checks to the more direct variant.