[clang] [clang][HIP] Make some math not not work with AMDGCN SPIR-V (PR #128360)

[Nico Weber via cfe-commits]

nico wrote:

This seems to break tests: http://45.33.8.238/linux/161683/step_6.txt

Please take a look and revert for now if it takes a while to fix.

https://github.com/llvm/llvm-project/pull/128360