[MLIR] NFC. Pass affine copy options by const ref

[bondhugula]

Summary

NFC. Pass affine copy options by const ref.

[bondhugula]

Trivial fix; self accepting.

mlir/lib/Dialect/Affine/Utils/LoopUtils.cpp

 /// `nBegin` is set to its replacement (set to `begin` if no invalidation
 /// happens). Since outgoing copies could have  been inserted at `end`, the
 /// output argument `nEnd` is set to the new end. `sizeInBytes` is set to the
 /// size of the fast buffer allocated.
 static LogicalResult generateCopy(
     const MemRefRegion &region, Block *block, Block::iterator begin,
     Block::iterator end, Block *copyPlacementBlock,
     Block::iterator copyInPlacementStart, Block::iterator copyOutPlacementStart,
-    AffineCopyOptions copyOptions, DenseMap<Value, Value> &fastBufferMap,
+    const AffineCopyOptions &copyOptions, DenseMap<Value, Value> &fastBufferMap,
     DenseSet<Operation *> &copyNests, uint64_t *sizeInBytes,
     Block::iterator *nBegin, Block::iterator *nEnd) {
   *nBegin = begin;
   *nEnd = end;
 
   func::FuncOp f = begin->getParentOfType<func::FuncOp>();
   OpBuilder topBuilder(f.getBody());
   Value zeroIndex = topBuilder.create<arith::ConstantIndexOp>(f.getLoc(), 0);