perf hists: Separate output fields parsing into setup_output_list function

perf hists: Separate output fields parsing into setup_output_list function

Separating output fields parsing into setup_output_list function, so
it's separated from field_order string setup and could be reused later
in following patches.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1453109064-1026-14-git-send-email-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>