Support for custom input_size no work in Detector Yolo

**It only supports input_size 224.**

https://github.com/sipeed/maix_train/blob/762b9771f13d7a6a73ab0f71435b32d2c011c262/train/__init__.py#L258

~~~
detector = Detector(**input_shape=(224, 224, 3)**,
                                  datasets_zip=self.datasets_zip_path,
                                   datasets_dir=self.datasets_dir,  ...)
~~~