https://bugs.freedesktop.org/show_bug.cgi?id=109206
--- Comment #11 from matrix8967@gmail.com --- This is the exact same issue I had and the above solution for removing /lib/firmware/amdgpu/raven_dmcu.bin worked for me.
For Ubuntu Users on 4.20 you'll need to also run
sudo update-initramfs -u
to update the bootimage. Thanks Chris.