Add gfx908 to the list of per-default compiled architectures. (#27388)
Summary:
ROCm 2.8 added preliminary support for gfx908.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/27388
Differential Revision: D17767772
Pulled By: bddppq
fbshipit-source-id: 172daf5bb66d3db86a13e287059af4b9b90a7f57
