perf annotate stdio: Fix --show-total-period

We were showing the total number of samples, not the total period as
asked by the user, fix it.

Reported-by: Namhyung Kim <namhyung@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Martin Liška <mliska@suse.cz>
Cc: Milian Wolff <milian.wolff@kdab.com>
Link: http://lkml.kernel.org/n/tip-lh2nh89rtqn5x5vbfthw6qml@git.kernel.org
Fixes: 0c4a5bce

 ("perf annotate: Display total number of samples with --show-total-period")
[ split from a larger patch ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>