iris: Use the clear depth when emitting 3DSTATE_CLEAR_PARAMS.

Take the clear depth into account when IRIS_DIRTY_DEPTH_BUFFER is marked
as dirty.

Also update the blorp surface clear color.

v2: Use a single if (zres && zres->aux.bo) (Ken).

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/gallium/drivers/iris/iris_blit.c

@@ -253,6 +253,8 @@ iris_blorp_surf_for_resource(struct iris_vtable *vtbl,
          .reloc_flags = is_render_target ? EXEC_OBJECT_WRITE : 0,
          .mocs = vtbl->mocs(res->bo),
       };
+      surf->clear_color =
+         iris_resource_get_clear_color(res, NULL, NULL);
    }
 
    // XXX: ASTC