drm/amdgpu: add mmhub client support for yellow carp

To help debugging GPUVM page faults.

Acked-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>