[Keyboard] Fix compilation issues for yanghu Unicorne

[drashna]

Description

This is broken on master too, not sure if worth fixing there, since part of the breakage is i2c_init related.

• Fixes issues with i2c compiling, due to changes with i2c setup.
• Fixes oled callbacks

Types of Changes

• Bugfix
• Keyboard (addition or update)

Issues Fixed or Closed by This PR

• Tzarc CI

Checklist

• My code follows the code style of this project: C, Python
• I have read the PR Checklist document and have made the appropriate changes.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• [ x] I have tested the changes and verified that they work and don't break anything (as well as I can manage).