tools: tests: speed up continuous toggle test

tools: tests: speed up continuous toggle test

The continuous toggle test was recently changed to poll the line to
check for toggles, and so increase test reliability. Tighten up the
test timings so the test can now also run in a significantly shorter
time.

And, as it is now faster, add an extra edge just to be sure.

Note that the test does not need to catch every edge, it only has to
check that the line is in fact toggling.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>