drm/amdgpu/vcn:Add new register offset/mask for VCN

Add new register offset/mask for VCN to support
latest VCN implementation.

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