perf hists: Add missing update on filtered stats in hists__decay_entries()

When a filter is used for perf top, its hists->nr_non_filtered_entries
was not updated after it removed an entry in hists__decay_entries().
Also hists->stats.total_non_filtered_period was missed too.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/1398327843-31845-8-git-send-email-namhyung@kernel.org
Signed-off-by: Jiri Olsa <jolsa@kernel.org>