perf hists browser: Fix percentage update on key press

Currently 'perf top --tui' decrements percentage of all entries on any
key press.  This is because it adds total period as new samples are
added to hists.  As perf-top does it currently but added samples are not
passed to the display thread, the percentages are decresing
continuously.

So separate total period stat into a different variable so that it
cannot affect the output total period.  This new total period stats are
used only for calcualating callchain percent limit.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Wang Nan <wangnan0@huawei.com>
Fixes: 0f58474e ("perf hists: Update hists' total period when adding entries")
Link: http://lkml.kernel.org/r/1455631723-17345-2-git-send-email-namhyung@kernel.org


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