[NFC] Change LoopVectorizationCostModel::useOrderedReductions() to be a const function.

[ABataev]

Mark as [NFC] patch

[Mel-Chen]

ping

[fhahn]

LGTM, thanks!

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

public:
   /// Split reductions into those that happen in the loop, and those that happen
   /// outside. In loop reductions are collected into InLoopReductionChains.
   void collectInLoopReductions();
 
   /// Returns true if we should use strict in-order reductions for the given
   /// RdxDesc. This is true if the -enable-strict-reductions flag is passed,
   /// the IsOrdered flag of RdxDesc is set and we do not allow reordering
   /// of FP operations.
-  bool useOrderedReductions(const RecurrenceDescriptor &RdxDesc) {
+  bool useOrderedReductions(const RecurrenceDescriptor &RdxDesc) const {
     return !Hints->allowReordering() && RdxDesc.isOrdered();
   }
 
   /// \returns The smallest bitwidth each instruction can be represented with.
   /// The vector equivalents of these instructions should be truncated to this
   /// type.
   const MapVector<Instruction *, uint64_t> &getMinimalBitwidths() const {
     return MinBWs;