Allow passing cpu to CUDA RPC device maps (#57019)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/57019
Based on https://github.com/pytorch/pytorch/pull/56043
Test Plan: Imported from OSS
Reviewed By: anjali411
Differential Revision: D28169796
Pulled By: beauby
fbshipit-source-id: 7fcf623de07c74c4f1ab415b7e20b518876a567a
