[Bug] RGB Matrix is broken on GMMK Pro as of 0.17.0

[trwnh]

Describe the Bug

RGB Matrix is entirely broken. None of the RGB_* keycodes work, and none of the LEDs light up.

System Information

Keyboard: GMMK Pro
Revision (if applicable): Rev 1?
Operating system: Arch Linux 5.17.9-arch1-1
qmk doctor output:

$ qmk doctor
Ψ QMK Doctor is checking your environment.
Ψ CLI version: 1.1.0
Ψ QMK home: /home/trwnh/git/qmk
Ψ Detected Linux.
Ψ Git branch: master
Ψ Repo version: 0.16.9
Ψ All dependencies are installed.
Ψ Found arm-none-eabi-gcc version 12.1.0
Ψ Found avr-gcc version 12.1.0
⚠ We do not recommend avr-gcc newer than 8. Downgrading to 8.x is recommended.
Ψ Found avrdude version 7.0
Ψ Found dfu-util version 0.11
Ψ Found dfu-programmer version 0.7.2
Ψ Submodules are up to date.
Ψ QMK is ready to go, but minor problems were found

Any keyboard related software installed?

• AutoHotKey (Windows)
• Karabiner (macOS)
• Other:

Additional Context

• 0.16.9 works
• 0.17.0 is broken
• git bisect results in the following:

[44f1bd9b3a9185951c283ceb5eeb2ecc2be72418] ChibiOS 21.11.1 update. (#16251)

This implicates #16251 as the cause of the issue, most likely when that commit got merged from develop to master.