Revert "clang/AMDGPU: Restore O3 checks in default-attributes.hip (#115238)"
This reverts commit 889d67785905ea85cdb17b2bf2b4b6f010b641f5.
Caused the following build bot failures, author has failed to address:
https://lab.llvm.org/buildbot/#/builders/144/builds/11132
https://lab.llvm.org/buildbot/#/builders/46/builds/7541
https://lab.llvm.org/buildbot/#/builders/190/builds/9077
Please fix before recommitting.