[AMDGPU] Partially revert my llvm::less_second patch (#136615)
This patch partially reverts:
commit 5e1b0f97735083b6762834b83fdbb35e76002e03
Author: Kazu Hirata <kazu@google.com>
Date: Fri Apr 18 10:05:55 2025 -0700
to fix:
LLVM :: CodeGen/AMDGPU/sched-group-barrier-pipeline-solver.mir
LLVM :: CodeGen/AMDGPU/sched-group-barrier-pre-RA.mir
under LLVM_ENABLE_EXPENSIVE_CHECKS.