freedreno: a2xx: NIR backend
These patches replace the a2xx TGSI compiler with a NIR compiler.
It also adds several new features:
- gl_FrontFacing, gl_FragCoord, gl_PointCoord, gl_PointSize
- control flow (including loops)
- texture related features (LOD/bias, cubemaps)
- filling scalar ALU slot when possible
Edited by Jonathan Marek