[clang] [CIR] Add NYI for fmaximum/fminimum/fmaximum_num/fminimum_num atomics (PR #206502)

[Erich Keane via cfe-commits]

erichkeane wrote:

> LGTM
> 
> I'm working on atomic libcall support recently and I'll take the implementation of these intrinsics.

awesome, thank you! 

https://github.com/llvm/llvm-project/pull/206502