perf test: Fix hists related entries

That got broken by d3a72fd8 ("perf report: Fix indentation of
dynamic entries in hierarchy"), by using the evlist in setup_sorting()
without checking if it is NULL, as done in some 'perf test' entries:

  $ find tools/ -name "*.c" | xargs grep 'setup_sorting(NULL);'
  tools/perf/tests/hists_output.c:      setup_sorting(NULL);
  tools/perf/tests/hists_output.c:      setup_sorting(NULL);
  tools/perf/tests/hists_output.c:      setup_sorting(NULL);
  tools/perf/tests/hists_output.c:      setup_sorting(NULL);
  tools/perf/tests/hists_output.c:      setup_sorting(NULL);
  tools/perf/tests/hists_cumulate.c:    setup_sorting(NULL);
  tools/perf/tests/hists_cumulate.c:    setup_sorting(NULL);
  tools/perf/tests/hists_cumulate.c:    setup_sorting(NULL);
  tools/perf/tests/hists_cumulate.c:    setup_sorting(NULL);
  $

Fix it.

Before:

  [root@jouet ~]# perf test
  <SNIP>
  15: Test matching and linking multiple hists                 : FAILED!
  16: Try 'import perf' in python, checking link problems      : Ok
  17: Test breakpoint overflow signal handler                  : Ok
  18: Test breakpoint overflow sampling                        : Ok
  19: Test number of exit event of a simple workload           : Ok
  20: Test software clock events have valid period values      : Ok
  21: Test object code reading                                 : Ok
  22: Test sample parsing                                      : Ok
  23: Test using a dummy software event to keep tracking       : Ok
  24: Test parsing with no sample_id_all bit set               : Ok
  25: Test filtering hist entries                              : FAILED!
  26: Test mmap thread lookup                                  : Ok
  27: Test thread mg sharing                                   : Ok
  28: Test output sorting of hist entries                      : FAILED!
  29: Test cumulation of child hist entries                    : FAILED!
  <SNIP>

After the patch the above failed tests complete successfully.
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Fixes: d3a72fd8 ("perf report: Fix indentation of dynamic entries in hierarchy")
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/sort.c

@@ -2635,25 +2635,14 @@ static int __setup_output_field(void)
 	return ret;
 }
 
-int setup_sorting(struct perf_evlist *evlist)
+static void evlist__set_hists_nr_sort_keys(struct perf_evlist *evlist)
 {
-	int err;
-	struct hists *hists;
 	struct perf_evsel *evsel;
-	struct perf_hpp_fmt *fmt;
-
-	err = __setup_sorting(evlist);
-	if (err < 0)
-		return err;
-
-	if (parent_pattern != default_parent_pattern) {
-		err = sort_dimension__add("parent", evlist);
-		if (err < 0)
-			return err;
-	}
 
 	evlist__for_each(evlist, evsel) {
-		hists = evsel__hists(evsel);
+		struct perf_hpp_fmt *fmt;
+		struct hists *hists = evsel__hists(evsel);
+
 		hists->nr_sort_keys = perf_hpp_list.nr_sort_keys;
 
 		/*
@@ -2667,6 +2656,24 @@ int setup_sorting(struct perf_evlist *evlist)
 				hists->nr_sort_keys--;
 		}
 	}
+}
+
+int setup_sorting(struct perf_evlist *evlist)
+{
+	int err;
+
+	err = __setup_sorting(evlist);
+	if (err < 0)
+		return err;
+
+	if (parent_pattern != default_parent_pattern) {
+		err = sort_dimension__add("parent", evlist);
+		if (err < 0)
+			return err;
+	}
+
+	if (evlist != NULL)
+		evlist__set_hists_nr_sort_keys(evlist);
 
 	reset_dimensions();