[coreboot] Please test coreboot using laptops with kernel 6.1-rc# for a possible backlight regression

[Tim Crawford]

I have tested backlight controls on Pop!_OS 22.04 with Ubuntu mainline kernel 6.1-rc3 (as well as Windows 10) on the following:

- system76/oryp6 (CML-H)
- system76/lemp10 (TGL-U)
- system76/lemp11 (ADL-U)
- system76/oryp9 (ADL-P)

ADL requires hooking up the GMA controls [1], and the mainboards need to specify the gfx in devicetree. With these changes, `acpi_video0` is present and backlight controls work.

Everything else is working as expected. I don't have anything older than CML-H anymore to test on.

[1]: https://review.coreboot.org/c/coreboot/+/69076