[mlir][sparse] fix bugs in concatenate rewriter.

mlir/lib/Dialect/SparseTensor/Transforms/SparseTensorRewriting.cpp

for (Value input : op.getInputs()) {
       // Build a for op for each input tensor to append new values into the
       // output tensor.
       foreachOp = rewriter.create<ForeachOp>(
           loc, input, cooBuffer,
           [&](OpBuilder &builder, Location loc, ValueRange args, Value v,
               ValueRange reduc) {
             SmallVector<Value, 4> indices;
             for (int64_t i = 0; i < rank; i++) {
-              uint64_t dim =
-                  toStoredDim(getSparseTensorEncoding(input.getType()), i);
-              Value idx = args[dim];
+              Value idx = args[i];
               if (i == static_cast<int64_t>(conDim))
                 // transform coordinates on matching dim
                 idx = builder.create<arith::AddIOp>(loc, idx, offset);
               indices.push_back(idx);
             }
             auto t = builder.create<InsertOp>(loc, v, reduc.front(), indices);
             builder.create<sparse_tensor::YieldOp>(loc, t);
           });