[Triton-MLIR][Backend] Fix the order in linear/delinear and a few bugs in reduce conversion (#851)

1, fix the order in linearize/delinearize, which fix the error of order
in emitIndices;
2, fix the selecting of fast implementation in reduce codegen;
3, fix the redundant barrier in reduce codegen;
4, fix the index mapping of the second round of warp_shuffle in shuffle
version of reduce codegen.

Co-authored-by: Keren Zhou <kerenzhou@openai.com>

lib/Analysis/Allocation.cpp

@@ -77,7 +77,7 @@ SmallVector<unsigned> getScratchConfigForReduce(triton::ReduceOp op) {
   auto srcShape = srcTy.getShape();
   auto axis = op.axis();
 
-  bool fastReduce = axis == 1; // FIXME(Qingyi): The fastest-changing dimension
+  bool fastReduce = axis == srcLayout.getOrder()[0];
 
   SmallVector<unsigned> smemShape;
   for (auto d : srcShape)