test: test sandbox sound driver more rigorously

Consider unexpected values for frequency:

* negative frequency
* zero frequency
* frequency exceeding sampling frequency

As in these cases the sum of the samples is zero also check the count of
the samples.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
3 files changed