Move leader-sampling configuration in preparation for adding support for
leader sampling with AUX area events.

Committer notes:

It only makes sense when configuring an evsel that is part of an evlist,
so the only case where it is called outside perf_evlist__config(), in
some 'perf test' entry, is safe, and even there we should just use
perf_evlist__config(), but since in that case we have just one evsel in
the evlist, it is equivalent.

Also fixed up this problem:

  util/record.c: In function ‘perf_evlist__config’:
  util/record.c:223:3: error: too many arguments to function ‘perf_evsel__config_leader_sampling’
    223 |   perf_evsel__config_leader_sampling(evsel, evlist);
        |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  util/record.c:170:13: note: declared here
    170 | static void perf_evsel__config_leader_sampling(struct evsel *evsel)
        |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lore.kernel.org/lkml/20200401101613.6201-14-adrian.hunter@intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>