Allow NO_PIN within data driven configuration

[zvecr]

Description

Mostly so that sparse DIRECT_PINS can be correctly configured without having to use a 1xN matrix.

Modifying mcu_pin does however allow other features to be incorrectly configured with NO_PIN. As an alternative solution, a new variant of mcu_pin_array could be introduced so that it limits the change to only matrix config.

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Keyboard (addition or update)
• Keymap/layout/userspace (addition or update)
• Documentation

Issues Fixed or Closed by This PR

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).