HDMI-CEC on Radxa Rock 5b+

See https://patchwork.kernel.org/project/linux-…@collabora.com/ for the main patches that added CEC support upstream, but there are follow-up fixes and everything becomes entwined in other DRM bridge work so backporting patches to an older kernel would be a painful task.

Thankfully current kernels have everything merged, so LE13 nightlies (6.18) and images in my test share (6.19) should have working HDMI-CEC support.