message: Update sort ops with neater test
diff: #include "tensorflow/compiler/xla/service/hlo_casting_utils.h"
  #include "tensorflow/compiler/xla/service/hlo_instructions.h"
  #include "tensorflow/compiler/xla/service/hlo_query.h"
  +#include "tensorflow/compiler/xla/service/pattern_matcher.h"
  #include <popops/ElementWise.hpp>
  #include <popops/Sort.hpp>
  namespace xla {
  +
  +namespace m = match;
  +
  namespace poplarplugin {
  namespace {
  bool IsSimpleComparison(const HloInstruction* inst) {
  HloInstruction* root(inst->to_apply()->root_instruction());
  - if (!hlo_query::AllOperandsAreParameters(*root)) {
  - return false;
  - }
  - if (root->opcode() != HloOpcode::kCompare) {
  + if (!Match(root, m::Compare(m::Parameter(0), m::Parameter(1)))) {
  return false;
  }
  