Fix isnan for integral types in MSVC (#33483)
Summary:
Fixes https://github.com/pytorch/pytorch/pull/32537#discussion_r381077989.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/33483
Differential Revision: D19970623
Pulled By: anjali411
fbshipit-source-id: 53502101822672a333ab5349d93b6e93f7ee4265
