Add matrix.c to sources for Keychron Q2

[selmanj]

Description

This change simply re-adds matrix.c to SRC in the Keychron Q2's rules.mk file for all keyboard revisions. It was removed in #15946, although I don't fully understand why. The PR comment says:

Delete matrix.c, Because we have replaced the resistor R7 from 10KΩ to 100KΩ on hardware so that we can reuse the boot pin of stm32l432 as a gerneral IO.

However without this file included the arrow keys no longer work (as reported in #16097). It would be ideal if @lalalademaxiya1 could confirm this file shouldn't have been removed.

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

• Fixes one issue in 16097

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).

[tzarc]

Would it be possible to give this commit a try instead of your fix?
aebece5

It's a core-side change, but should be much more maintainable than requiring a custom matrix implementation.

[selmanj]

@tzarc Just tried it on my Q2 and it works. That's a much cleaner solution - I'm happy to close this PR in favor of that commit.

[tzarc]

@tzarc Just tried it on my Q2 and it works. That's a much cleaner solution - I'm happy to close this PR in favor of that commit.

Perfect, I'll sort out a corresponding PR. Would be great if you could give it a thumbs-up after!

[tzarc]

Raised PR #16278.

[selmanj]

Closing in favor of #16278