[LegalizeDAG][RISCV][PowerPC][AMDGPU][WebAssembly] Improve expansion of SETONE/SETUEQ...

[LegalizeDAG][RISCV][PowerPC][AMDGPU][WebAssembly] Improve expansion of SETONE/SETUEQ on targets without SETO/SETUO.

If SETO/SETUO aren't legal, they'll be expanded and we'll end up
with 3 comparisons.

SETONE is equivalent to (SETOGT || SETOLT)
so if one of those operations is supported use that expansion. We
don't need both since we can commute the operands to make the other.

SETUEQ can be implemented with !(SETOGT || SETOLT) or (SETULE && SETUGE).
I've only implemented the first because it didn't look like most of the
affected targets had legal SETULE/SETUGE.

Reviewed By: frasercrmck, tlively, nemanjai

Differential Revision: https://reviews.llvm.org/D94450