modstruct: Rename module to "ustruct", to allow full Python-level impl.
diff --git a/py/objmodule.c b/py/objmodule.c
index c67a9b2..e0fad37 100644
--- a/py/objmodule.c
+++ b/py/objmodule.c
@@ -142,7 +142,7 @@
     { MP_OBJ_NEW_QSTR(MP_QSTR__collections), (mp_obj_t)&mp_module_collections },
 #endif
 #if MICROPY_PY_STRUCT
-    { MP_OBJ_NEW_QSTR(MP_QSTR_struct), (mp_obj_t)&mp_module_struct },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_ustruct), (mp_obj_t)&mp_module_ustruct },
 #endif
 
 #if MICROPY_PY_BUILTINS_FLOAT