[libclc] [libclc] Refine __clc_fp*_subnormals_supported and __clc_flush_denormal_if_not_supported (PR #157633)

[Matt Arsenault via cfe-commits]

https://github.com/arsenm commented:

I think dropping the soft FMA is beyond the scope of this patch, but it is something I think should be done 

https://github.com/llvm/llvm-project/pull/157633