perf tools: Properly set the value of 'old' and 'head' in snapshot mode

This patch adds the necessay intelligence to properly compute the value
of 'old' and 'head' when operating in snapshot mode.  That way we can get
the latest information in the AUX buffer and be compatible with the
generic AUX ring buffer mechanic.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
1 file changed