vulkan/wsi: misc cleanups and fixes
Here's a few cleanups and fixes that corrects a couple of mistakes in the current WSI implementations:
- We were missing barriers around the PRIME blit, violating the vulkan spec
- We were assuming optimal-tiling was actually linear in the Win32 code-path
Neither of these seems to have been real problems until now, but with the introduction of Dozen, these becomes real problems.