Move the CUDA implementation of log to ATen. (#26494)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/26494
Close #24586
Test Plan: Imported from OSS
Differential Revision: D17572497
Pulled By: VitalyFedyunin
fbshipit-source-id: e1bcd33021464eaa4affd4c6d3283c8403069945
