Revert "[RISCV] Fix reporting of incorrect commutable operand indices"

This reverts commit a793329.

This commit caused some bot failures:

clang-with-thin-lto-ubuntu-release
lld-x86_64-win-release
llvm-clang-x86_64-expensive-checks-debian-release

Author: tstellar

llvm/lib/Target/RISCV/RISCVInstrInfo.cpp

@@ -1223,7 +1223,7 @@ bool RISCVInstrInfo::findCommutedOpIndices(const MachineInstr &MI,
         // Both of operands are not fixed. Set one of commutable
         // operands to the tied source.
         CommutableOpIdx1 = 1;
-      } else if (SrcOpIdx1 == CommuteAnyOperandIndex) {
+      } else if (SrcOpIdx1 == CommutableOpIdx1) {
         // Only one of the operands is not fixed.
         CommutableOpIdx1 = SrcOpIdx2;
       }