drm/amdgpu/nbio: add vcn doorbell multiple AIDs support

Update vcn doorbell range 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>