audiofuntest: set capture buffer size to 3 periods to avoid overrun

Set capture buffer size to 3 periods to avoid overrun in some platform.

BUG=chrome-os-partner:52117
TEST=None

Change-Id: Icda91118629ab3dd57df21be9735d5b58e178800
Signed-off-by: Shun-Hsing Ou <shunhsingou@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/340265
Commit-Ready: Nicolas Boichat <drinkcat@chromium.org>
Reviewed-by: Ben Zhang <benzh@chromium.org>
1 file changed