RadeonSI Goes Rusticl-Only, Clearing Out Support For Old Clover OpenCL

Earlier this month Mesa deprecated the Clover OpenCL driver in favor of the modern Rust-written Rusticl Gallium3D state tracker. Clover is expected to be removed in Q3's Mesa 25.2 release while today the RadeonSI driver has decided to preemptively remove its Clover support...