* [Feature] Add kenerl updation for some decoder heads.

* [Feature] Add kenerl updation for some decoder heads.

* directly use forward_feature && modify other 3 decoder heads

* remover kernel_update attr

* delete unnecessary variables in forward function

* delete kernel update function

* delete kernel update function

* delete unnecessary docstrings

* modify comments in self._forward_feature()

* modify docstrings in self._forward_feature()

* fix docstring

* modify uperhead