[libclc] libclc: Replace nextafter implementation (PR #186082)

[Romaric Jodin via cfe-commits]

rjodinchr wrote:

This implementation is not passing on various platforms.

I think it does not handle Flush-To-Zero (FTZ) nor Denormals-Are-Zero (DAZ) behaviors.

I think we need to revert back to the previous implementation. Is that possible?

https://github.com/llvm/llvm-project/pull/186082