[llvm] SelectionDAG: Use qNaN constant if FCANONICALIZE not LegalOrCustom (PR #104564)

[YunQiang Su via llvm-commits]

wzssyqa wrote:

> > @arsenm is it acceptable if we don't require keeping payload?
> 
> Yes. Payload preservation is a nice to have, not a requirement

I mean this patch, if I drop the test cases of X86 and set canonicalize of x86 as Expand.

https://github.com/llvm/llvm-project/pull/104564