dm stats: report precise_timestamps and histogram in @stats_list output

dm stats: report precise_timestamps and histogram in @stats_list output

commit bd49784fd1e8f42c7600fbfa206361324857f373 upstream.

If the user selected the precise_timestamps or histogram options, report
it in the @stats_list message output.

If the user didn't select these options, no extra tokens are reported,
thus it is backward compatible with old software that doesn't know about
precise timestamps and histogram.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # 4.2
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>