perf top: Decay all events in the evlist

perf top: Decay all events in the evlist

Currently perf top only decays entries in a selected evsel.  I don't
know whether it's intended (maybe due to performance reason?) but anyway
it might show incorrect output when event group is used since users will
see leader event is decayed but others are not.

This patch moves the decay code into perf_top__resort_hists() so that
stdio and TUI code shared the logic.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/20190827231555.121411-1-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>