[clang] clang/HIP: Remove __ockl_fdot2 declaration (PR #201878)

[via cfe-commits]

ronlieb wrote:

> Hello! This PR seems to break our two HIP bots. Reverting this commit in my local test resolved the issue.
> 
> https://lab.llvm.org/buildbot/#/builders/230/builds/1821 https://lab.llvm.org/buildbot/#/builders/232/builds/1544

Hi Kewen, i think we need to update the buildbot to use newer rocm-systems sha
https://github.com/ROCm/rocm-systems/pull/2230

https://github.com/llvm/llvm-project/pull/201878