Change DRIVER_LED_COUNT to {LED,RGB}_MATRIX_LED_COUNT

[fauxpark]

Description

Allows for this config define to be moved to info.json.

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).

[fauxpark]

Lint errors are unrelated.

☒ geekboards/macropad_v2: Layout "LAYOUT" has no "matrix" definition in either "info.json" or "<keyboard>.h"!
☒ spaceholdings/nebula12: Layout "LAYOUT_68_ansi" has no "matrix" definition in either "info.json" or "<keyboard>.h"!

[Kriechi]

@fauxpark how does this related to #18036 in any way by chance?

[fauxpark]

The ws2812.h change would need to be updated (assuming this PR is merged first), other than that there is nothing else to do there.