[libclc] [libclc] Reduce bithacking in CLC frexp (PR #129871)

[Romaric Jodin via cfe-commits]

rjodinchr wrote:

I'm clearly seeing those devices returning true when comparing subnormals to zero. So either they all have a bug, or the SPIR-V code produced by `clspv` is buggy.
If it ends up being a bug from the device, we might want to have something more architecture friendly, or at least a way to fallback on a less efficient but always working implementation.
Let's hope it can be dealt with clspv

https://github.com/llvm/llvm-project/pull/129871