Fix issue with dispatch key: AutogradXPU (#56336)
Summary:
Automatically add dispatch key "AutogradXPU" with "xpu" tensor. And set "fall through" for AutogradXPU
Pull Request resolved: https://github.com/pytorch/pytorch/pull/56336
Reviewed By: heitorschueroff
Differential Revision: D27872125
Pulled By: ailzhang
fbshipit-source-id: c120c62becd577699f9aecb4c356c889bd37ad06
