Clarify meaning of `pin_memory_device` argument (#94349)
I don't think the docstring explaining `pin_memory_device` is very clear. If it weren't for the string type, I would not have guessed that this was about the device that is referred to in the `pin_memory` option (and honestly, it took me a few minutes before noticing the type).
Pull Request resolved: https://github.com/pytorch/pytorch/pull/94349
Approved by: https://github.com/ejguan
