drm/amdgpu: enable display for cyan skillfish

Display support for cyan skillfish is ready now. Enable it!

Signed-off-by: Lang Yu <lang.yu@amd.com>
Reviewed-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>