[X86] combineCarryThroughADD - add support for X86::COND_A commutations (PR24545)

As discussed on PR24545, we should try to commute X86::COND_A 'icmp ugt' cases to X86::COND_B 'icmp ult' to more optimally bind the carry flag output to a SBB instruction.

Differential Revision: https://reviews.llvm.org/D57281

llvm-svn: 352289