Let logspace support bfloat16 on both CPU and CUDA (#44675)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/44675
Reviewed By: ngimel
Differential Revision: D23710801
Pulled By: mruberry
fbshipit-source-id: 12d8e56f41bb635b500e89aaaf5df86a1795eb72
