drm/amdgpu: add vangogh asic header files (v2)

This patch is to add vangogh asic header files.

v2: squash in updates

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