fix pybind issue for get_autocast_cpu_dtype and get_autocast_gpu_dtype (#66396)
Summary:
There has an issue when calling **torch.get_autocast_cpu_dtype** and **torch.get_autocast_gpu_dtype**:
```
>>> torch.get_autocast_gpu_dtype()==torch.half
False
>>> torch.get_autocast_cpu_dtype()==torch.bfloat16
False
```
but the expected results should be :
```
>>> torch.get_autocast_gpu_dtype()==torch.half
True
>>> torch.get_autocast_cpu_dtype()==torch.bfloat16
True
```
This PR is about fixing this issue.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/66396
Reviewed By: ejguan
Differential Revision: D31541727
Pulled By: albanD
fbshipit-source-id: 1a0fe070a82590ef2926a517bf48046c2633d168
