perf top: Delete half-processed hist entries when exit

After sample processing is done, hist entries are in both of
hists->entries and hists->entries_in (or hists->entries_collapsed).  So
I guess perf report does not have leaks on hists.

But for perf top, it's possible to have half-processed entries which are
only in hists->entries_in.  Eventually they will go to the
hists->entries and get freed but they cannot be deleted by current
hists__delete_entries().  This patch adds hists__delete_all_entries
function to delete those entries.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-and-Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1449734015-9148-2-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>