dbr quant: extend qconfig_dict support to functionals, part 2 (#69766)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/69766
Follow-up on the previous PR, removes the requirement to have a parent
qconfig in order for the object type qconfig to be applied for a function.
Test Plan:
```
python test/test_quantization.py TestQuantizeDBR
```
Reviewed By: jerryzh168
Differential Revision: D33020218
Pulled By: vkuzo
fbshipit-source-id: fa0e10f05ca5f88b48ef74b9d2043ea763506742
