dbr quant: support functional linear without bias (#70328)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/70328
Currently linear with bias crashes DBR convert step, this PR fixes it.
This unbreaks testing DBR on some customer models.
Test Plan:
```
python test/test_quantization.py TestQuantizeDBRIndividualOps.test_linear_functional_nobias
```
Reviewed By: jerryzh168
Differential Revision: D33285311
Pulled By: vkuzo
fbshipit-source-id: 757c7270be9e3ff9cdf2609b1e426e9fd34e50ff
