[quant][graphmode][fx] Support quantization for custom module (#44074)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/44074
Test Plan: Imported from OSS
Reviewed By: vkuzo
Differential Revision: D23580642
fbshipit-source-id: a80b0b3e5e1f4c4a9647da872239cc0a4d58dd3b
