[Keyboard] Fixup Neson Design N6 ISSI includes

[drashna]

Description

Fix the include/src paths for the ISSI drivers for the keyboard, due to changes on develop.

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.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).