[quant] Regsiter fake_quant and observer attributes as buffers (#33626)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/33626
For DDP we require the attributes to be registered as buffers. By doing this the value is broadcast from one device to the rest.
Test Plan:
Tested on actual model on GPU
Imported from OSS
Differential Revision: D20038839
fbshipit-source-id: 82e829fc3baca0b3262c3894a283c375eb08a4a4
