nir: Remove old-school deref chain support

Acked-by: Rob Clark <robdclark@gmail.com>
Acked-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Acked-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/compiler/nir/nir_lower_io.c

@@ -510,8 +510,6 @@ nir_lower_io(nir_shader *shader, nir_variable_mode modes,
 {
    bool progress = false;
 
-   nir_assert_unlowered_derefs(shader, nir_lower_load_store_derefs | nir_lower_interp_derefs | nir_lower_atomic_derefs);
-
    nir_foreach_function(function, shader) {
       if (function->impl) {
          progress |= nir_lower_io_impl(function->impl, modes,