[fx const fold] fix a case when some inputs are unused (#65223)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/65223
If there're unused inputs, they won't appear in `submod_1`. We need to add all the unused inputs so that the model after const fold has the same inputs as the original model.
Reviewed By: jfix71
Differential Revision: D31021217
fbshipit-source-id: b7452c90d133b747e0699936a81d3fee14af9cc9
