nir: Call nir_metadata_preserve on !progress

Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5171>

src/compiler/nir/nir_lower_scratch.c

@@ -175,6 +175,8 @@ nir_lower_vars_to_scratch(nir_shader *shader,
          progress = true;
          nir_metadata_preserve(function->impl, nir_metadata_block_index |
                                                nir_metadata_dominance);
+      } else {
+         nir_metadata_preserve(function->impl, nir_metadata_all);
       }
    }