turnip: effectively enable gmem rendering with DXVK
requested to merge Danil/mesa:turnip/perf/delay-gmem-render-decision-for-subpass-self-deps into main
DXVK always inserts vertex stage subpass self-dependency for every
subpass regardless of whether there actually would be a barrier.
This effectively disabled gmem rendering with DXVK.
See https://github.com/doitsujin/dxvk/blob/a58feaa16ec06e5a8368eecc45b0ffe50058ca4c/src/dxvk/dxvk_renderpass.cpp#L190-L199
Thus we delay the decision to disable gmem rendering until we see a barrier with vertex stages.
Does this improve performance with DXVK? It's hard to tell...