Keebio RGB wiring update

[nooges]

Description

Change configuration for Keebio split boards to use the same RGB strip wiring for each half, which provides the following improvements:

1. Easier wiring due to one fewer wire needed (the wire between left DOut to extra data pin) and the fact that wiring is the same for both halves.
2. RGB LEDs can be controlled by each half now instead of just master half.
3. Extra data line is freed up to allow for I2C usage instead of serial.

Keebio docs have also been updated already to reflect new wiring setup.

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.
• 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).

[zvecr]

Tagging as "breaking change" till we work out what the impact is.

[SethBarberee]

Looks like my keymap for the iris gives an error since I define RGBLED_SPLIT. You've got my permission to modify the keymap if you need to, @nooges

[nooges]

@SethBarberee I'll test out adding a check to see if RGBLED_SPLIT is already defined by the user to get rid of the impact on keymaps.

[bcat]

My Quefrency keymap has the same problem. Feel free to toss an #undef RGBLED_SPLIT into said keymap to fix this.

[nooges]

Note to self: add #undef RGBLED_SPLIT to user keymaps as needed

[nooges]

Rebased PR on top of develop and checked that the affected users using their own #define RGBLED_SPLIT have #undef.

[noroadsleft]

Looks good to me.

[noroadsleft]

Thanks!