py/objint_longlong: Add stub for mp_obj_int_from_bytes_impl().

To be implemented later.

py/objint_longlong.c

@@ -53,6 +53,10 @@
 const mp_obj_int_t mp_maxsize_obj = {{&mp_type_int}, MP_SSIZE_MAX};
 #endif
 
+mp_obj_t mp_obj_int_from_bytes_impl(bool big_endian, size_t len, const byte *buf) {
+    mp_not_implemented("");
+}
+
 void mp_obj_int_to_bytes_impl(mp_obj_t self_in, bool big_endian, size_t len, byte *buf) {
     assert(MP_OBJ_IS_TYPE(self_in, &mp_type_int));
     mp_obj_int_t *self = self_in;