move min/max tests to TestTorchDeviceType (#41908)
Summary:
so that testing _min_max on the different devices is easier, and min/max operations have better CUDA test coverage.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/41908
Reviewed By: mruberry
Differential Revision: D22697032
Pulled By: ngimel
fbshipit-source-id: a796638fdbed8cda90a23f7ff4ee167f45530914
