disable "tp_reserved" usage in PyPy (part 2)

Cython/Utility/Coroutine.c

@@ -103,7 +103,7 @@ static CYTHON_INLINE PyObject *__Pyx_Coroutine_GetAwaitableIter(PyObject *o) {
 // adapted from genobject.c in Py3.5
 static PyObject *__Pyx__Coroutine_GetAwaitableIter(PyObject *obj) {
     PyObject *res;
-#if PY_MAJOR_VERSION >= 3
+#if CYTHON_COMPILING_IN_CPYTHON && PY_MAJOR_VERSION >= 3
     __Pyx_PyAsyncMethodsStruct* am = __Pyx_PyType_AsAsync(obj);
     if (likely(am && am->am_await)) {
         res = (*am->am_await)(obj);