CTS tests both layered and separate DPB, but radv wasn't handling
layered properly when used with the tier 2 dpb handling.
This adjusts the addresses to use the layer index for tier2.
Fixes dEQP-VK.video.decode.*layered*
Cc: mesa-stable
Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/29758>