https://bugs.freedesktop.org/show_bug.cgi?id=105619
--- Comment #11 from freedesktop@kp-tech.hu --- None of the graphics display working (DVI, VGA) on EL7 + ROCM 1.8 beta. At least on 4.15 the DVI output was worked. It seems that this issue will not going to be fixed, just disable the amdgpu support for Kaveri:
Don't default to DC support for Kaveri and older: https://lists.freedesktop.org/archives/amd-gfx/2018-May/022021.html