[X86] SimplifyDemandedVectorEltsForTargetNode should be calling resolveTargetShuffleInputs not getTargetShuffleMask

Add TODO comment.

llvm-svn: 367318

llvm/lib/Target/X86/X86ISelLowering.cpp

@@ -34293,6 +34293,7 @@ bool X86TargetLowering::SimplifyDemandedVectorEltsForTargetNode(
   }
 
   // Simplify target shuffles.
+  // TODO: Use resolveTargetShuffleInputs.
   if (!isTargetShuffle(Opc) || !VT.isSimple())
     return false;