Fix incorrect usage of __HIP_PLATFORM_HCC__ (#21757)
Summary:
This avoid using `__HIP_PLATFORM_HCC__` in case it changes in the future.
Following up https://github.com/pytorch/pytorch/issues/21718
Pull Request resolved: https://github.com/pytorch/pytorch/pull/21757
Reviewed By: xw285cornell
Differential Revision: D15891867
Pulled By: bddppq
fbshipit-source-id: 5de55687ab1c86eddf6b4d8d25fee48d96ec72ad
