gallium/radeon: make it clear that DRM 2.x.x fast clear constraint is CIK-only
gallium/radeon: make it clear that DRM 2.x.x fast clear constraint is CIK-only

Reviewed-by: Nicolai Hähnle <0d0be6cf5ad662651be2dc5dfd44aa2b09d4c1cc@amd.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler