drm/amdgpu/vcn: update vcn header to support multiple AIDs

Add aid_id in vcn header to support multiple AIDs

Signed-off-by: James Zhu <James.Zhu@amd.com>
Acked-by: Leo Liu <leo.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>