perf report: Enable group view with hierarchy

Now that all the missing pieces are implemented, let's enable it.  An
example output below:

  $ perf record -e '{cycles,instructions}' make
  $ perf report --hierarchy --stdio
  ...
  #               Overhead  Command / Shared Object / Symbol
  # ......................  ..................................
  #
  ...
      25.74%  27.18%        sh
         19.96%  24.14%        libc-2.24.so
            9.55%  14.64%        [.] __strcmp_sse2
            1.54%   0.00%        [.] __tfind
            1.07%   1.13%        [.] _int_malloc
            0.95%   0.00%        [.] __strchr_sse2
            0.89%   1.39%        [.] __tsearch
            0.76%   0.00%        [.] strlen
  ...

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Requested-by: Andi Kleen <andi@firstfloor.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20160913074552.13284-8-namhyung@kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>