[quant] Mapping for the `_LinearWithBias` (#49964)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/49964
`torch.nn.modules.linear._LinearWithBias` is only used in the transformers, and is completely identical to the `torch.nn.Linear`.
This PR creates a mapping so that this module would be treated the same as the Linear.
Test Plan:
```
python test/test_quantization.py TestDynamicQuantizedModule TestStaticQuantizedModule
```
Differential Revision: D25731589
Reviewed By: jerryzh168
Pulled By: z-a-f
fbshipit-source-id: 1b2697014e250e97d3010cdb542f9d130b71fbc3
