radeonsi/vcn: Add decode DPB buffers as CS dependency
What does this MR do and why?
radeonsi/vcn: Add decode DPB buffers as CS dependency
This is needed to ensure correct synchronization in kernel eg. when it
moves the buffers between VRAM and GTT.
Cc: mesa-stable
Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/3437
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/11624