Same error with Kabylake/eve:

[    3.552219] i915 0000:00:02.0: Direct firmware load for i915/kbl_dmc_ver1_01.bin failed with error -2
[    3.553624] i915 0000:00:02.0: Failed to load DMC firmware [https://01.org/linuxgraphics/downloads/firmware], disabling runtime power management.

This is a known issue: UPSTREAM doesn't support the following combination:

   built-in driver + firmware not built-in

You need the following CHROMIUM patch: https://chromium-review.googlesource.com/q/I7ded154b4ae6003d32e87d3a620

It was merged in chromeos-4.14 in January 11, so this is hopefully fixed now.

Upstream discussion referenced in:
https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/354089

If I recall correctly, this was a version issue (we didn't provide the necessary FW versions), but I'll need to retest.

Based on the timestamp of the logs I now think you're right, sorry for the confusion.

BTW a generic discussion about hardcoding the DMC firmware version can be found here:
https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/751805