zephyr: Support time -> utime module "weaklink".

So, now it's possible to just do normal Python's "import time".

zephyr/mpconfigport.h

@@ -54,6 +54,7 @@
 #define MICROPY_PY_IO               (0)
 #define MICROPY_PY_MICROPYTHON_MEM_INFO (1)
 #define MICROPY_PY_MACHINE          (1)
+#define MICROPY_MODULE_WEAK_LINKS   (1)
 #define MICROPY_PY_STRUCT           (0)
 #define MICROPY_PY_UTIME            (1)
 #define MICROPY_PY_UTIME_MP_HAL     (1)
@@ -104,6 +105,9 @@ extern const struct _mp_obj_module_t mp_module_time;
     { MP_OBJ_NEW_QSTR(MP_QSTR_machine), (mp_obj_t)&mp_module_machine }, \
     MICROPY_PY_UTIME_DEF \
 
+#define MICROPY_PORT_BUILTIN_MODULE_WEAK_LINKS \
+    { MP_OBJ_NEW_QSTR(MP_QSTR_time), MP_ROM_PTR(&mp_module_time) }, \
+
 // extra built in names to add to the global namespace
 #define MICROPY_PORT_BUILTINS \
     { MP_OBJ_NEW_QSTR(MP_QSTR_help), (mp_obj_t)&mp_builtin_help_obj }, \