perf hists: Fix dynamic entry display in hierarchy

When dynamic sort key is used it might not show pretty printed output.
This is because the trace output was not set only for the first dynamic
sort key.  During hierarchy_insert_entry() it missed to pass the
trace_output to dynamic entries.  Also even if it did, only first entry
will have it.  Subsequent entries might set it during collapsing stage
but it's not guaranteed.

Before:

  $ perf report --hierarchy --stdio -s ptr,bytes_req,gfp_flags -g none
  #
  #       Overhead  ptr / bytes_req / gfp_flags
  # ..............  ..........................................
  #
      37.50%        0xffff8803f7669400
         37.50%        448
            37.50%        66080
      10.42%        0xffff8803f766be00
          8.33%        96
             8.33%        66080
          2.08%        512
             2.08%        67280

After:

  #
  #       Overhead  ptr / bytes_req / gfp_flags
  # ..............  ..........................................
  #
      37.50%        0xffff8803f7669400
         37.50%        448
            37.50%        GFP_ATOMIC|GFP_NOWARN|GFP_NOMEMALLOC
      10.42%        0xffff8803f766be00
          8.33%        96
             8.33%        GFP_ATOMIC|GFP_NOWARN|GFP_NOMEMALLOC
          2.08%        512
             2.08%        GFP_KERNEL|GFP_NOWARN|GFP_REPEAT|GFP

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1456512767-1164-4-git-send-email-namhyung@kernel.org


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