message: Remove recursive check for master in unsort_matrix
diff: @@ -61,24 +61,11 @@ void unsort_matrix(matrix::Csr<ValueType, IndexType> *mtx,
  return;
  }
  const auto &exec = mtx->get_executor();
  - auto master = mtx->get_executor()->get_master();
  + const auto &master = exec->get_master();
  // If exec is not the master/host, extract the master and perform the
  // unsorting there, followed by copying it back
  if (exec != master) {
  - constexpr int max_depth{10}; // Max depth that is searched for master
  - bool actual_master_found{false};
  - for (int i = 0; i < max_depth; ++i) {
  - const auto new_master = master->get_master();
  - if (new_master == master) {
  - actual_master_found = true;
  - break;
  - }
  - master = new_master;
  - }
  - if (!actual_master_found) {
  - GKO_NOT_SUPPORTED(exec);
  - }
  auto h_mtx = mtx->clone(master);
  unsort_matrix(lend(h_mtx), engine);
  mtx->copy_from(lend(h_mtx));
  @@ -110,37 +97,22 @@ void unsort_matrix(matrix::Coo<ValueType, IndexType> *mtx,
  using value_type = ValueType;
  using index_type = IndexType;
  auto nnz = mtx->get_num_stored_elements();
  -
  if (nnz <= 0) {
  return;
  }
  const auto &exec = mtx->get_executor();
  - auto master = mtx->get_executor()->get_master();
  + const auto &master = exec->get_master();
  // If exec is not the master/host, extract the master and perform the
  // unsorting there, followed by copying it back
  if (exec != master) {
  - constexpr int max_depth{10}; // Max depth that is searched for master
  - bool actual_master_found{false};
  - for (int i = 0; i < max_depth; ++i) {
  - const auto new_master = master->get_master();
  - if (new_master == master) {
  - actual_master_found = true;
  - break;
  - }
  - master = new_master;
  - }
  - if (!actual_master_found) {
  - GKO_NOT_SUPPORTED(exec);
  - }
  auto h_mtx = mtx->clone(master);
  unsort_matrix(lend(h_mtx), engine);
  mtx->copy_from(lend(h_mtx));
  return;
  }
  -
  auto vals = mtx->get_values();
  auto rows = mtx->get_row_idxs();
  auto cols = mtx->get_col_idxs();
  