panfrost: LogicOp support
The generated shaders are definitely not optimal, but for a feature hardly anyone uses, it's probably good enough.
The XScreensaver demo quasicrystal now works.
The XScreensaver demos blitspin, bouboule and also crystal work, but because they use LogicOp indirectly through X with Glamor, testing should be done in a nested Wayland compositor.
Currently this only works for 8-bit textures.