perf hists browser: Fix indentation of folded sign on --hierarchy

It should indent 2 spaces for folded sign and a whitespace.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20161108130833.9263-2-namhyung@kernel.org


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