perf tools: Recalc total periods using top-level entries in hierarchy

When hierarchy mode is enabled, each entry in a hierarchy level shares
the period.  IOW an upper level entry's period is the sum of lower level
entries.  Thus perf uses only one of them to calculate the total period
of hists.  It was lowest-level (leaf) entries but it has a problem when
it comes to filters.

If a filter is applied, entries in the same level will be filtered or
not.  But upper level entries still have period of their sum including
filtered one.  So total sum of upper level entries will not be same as
sum of lower level entries.

This resulted in entries having more than 100% of overhead and it can be
produced using perf top with filter(s).

Reported-and-Tested-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Namhyung Kim <namhyung@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/1457531222-18130-8-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>