alsa_api_test: Check device consumption rate

The sleep time in each period might not be accurate.
Check device consumption rate rather than checking buffer level.

BUG=chromium:617516
TEST=run alsa_api_test --move on samus.

Change-Id: I6d60c7839717a485fbe744dd6500041cbdcebfd6
Reviewed-on: https://chromium-review.googlesource.com/357691
Commit-Ready: Cheng-Yi Chiang <cychiang@chromium.org>
Tested-by: Cheng-Yi Chiang <cychiang@chromium.org>
Reviewed-by: Hsinyu Chao <hychao@chromium.org>
1 file changed