turnip: add an initial non-conformant vulkan driver for adreno

Hi,

This is an early Vulkan driver for Adreno A6xx GPU family. Actually, it is so early that it only renders a very specific triangle. But instead of keeping developing it in a personal repo, we feel it is better to develop it upstream... to make the (interesting?) early history easily accessible, to have a wider audience, and more importantly, why not?

This driver is in no way conformant. It is also not to be tested out by adventurous users yet, because they might only find disappointments in such an early driver. But feedback/contributions as the development goes on are highly welcomed.

Thanks to Bas, Chad, Kristian, Robert, and others who work on this driver together. The driver also uses many common code developed for anv, radv, and especially freedreno.

CC: @bnieuwenhuizen @chadversary @krh @robclark