Adding lost extra_repr() and __setstate __() to activation.py (#39084)
Summary:
Add
```python
def __setstate__(self, state):
self.__dict__.update(state)
if not hasattr(self, 'dim'):
self.dim = None
def extra_repr(self):
return 'dim={dim}'.format(dim=self.dim)
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/39084
Differential Revision: D21825245
Pulled By: albanD
fbshipit-source-id: c790c288a9b23e7f320a912e21397da16bb1fb5a
