RadeonSI May Eventually Switch To NIR Completely

RadeonSI developers have been working on supporting the NIR intermediate representation within their Gallium3D driver as a means to support ARB_gl_spirv for being able to load SPIR-V shaders in OpenGL and interact with the RADV Vulkan driver code paths, which is making use of NIR. It's looking like in the future the RadeonSI driver could end up using NIR completely by default...