[pytorch][ao] force weight observer/fake_quant to be on the same device as the weight tensor (#106755)
Summary:
As title.
There's a corner case where both cpu and gpu are avaiable, although the model is moved to cpu, the newly created PTQ weight observer is still on gpu. Therefore, during the convert, this line will fail https://fburl.com/4rhipfvb
Test Plan: CI
Differential Revision: D48141494
Pull Request resolved: https://github.com/pytorch/pytorch/pull/106755
Approved by: https://github.com/jerryzh168
