[clang] [clang][Driver]Fix opencl -cl-fast-relaxed-math flag to have similar behaviour as ffast-math (PR #208709)

[Matt Arsenault via cfe-commits]

arsenm wrote:

> > Raw CC1 invocations don't have an expectation of stability?
> 
> Yes, but -ffast-math still has old behavior in cc1. This PR only changes -cl-fast-relaxed-math. If everything is moved to driver, it will be very difficult for cc1 users that embed clang as frontend.

Users should not be directly using cc1 

https://github.com/llvm/llvm-project/pull/208709