[LegalizeIntegerTypes] Improve ExpandIntRes_SADDSUBO codegen on targets without SADDO/SSUBO.

This code creates 3 setccs that need to be expanded. It was
creating a sign bit test as setge X, 0 which is non-canonical.
Canonical would be setgt X, -1. This misses the special case in
IntegerExpandSetCCOperands for sign bit tests that assumes
canonical form. If we don't hit this special case we end up
with a multipart setcc instead of just checking the sign of
the high part.

To fix this I've reversed the polarity of all of the setccs to
setlt X, 0 which is canonical. The rest of the logic should
still work. This seems to produce better code on RISCV which
lacks a setgt instruction.

This probably still isn't the best code sequence we could use here.

Reviewed By: RKSimon

Differential Revision: https://reviews.llvm.org/D97181