alsa_conformance_test: Use available channels instead of channel range

The channel range may not show all channels we can use. For example, if
a device supports 2 and 4 channels, the channel range only shows 2 to 4.
Therefore, using available channels is better.

BUG=chromium:685077, b:138825293
TEST=It shows available channels correctly on eve.

Change-Id: I5006ec2016e9fe7cfa8b952627cc0f0c777bf506
Reviewed-on: https://chromium-review.googlesource.com/1789332
Tested-by: Yu-Hsuan Hsu <yuhsuan@chromium.org>
Commit-Ready: Yu-Hsuan Hsu <yuhsuan@chromium.org>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Reviewed-by: Cheng-Yi Chiang <cychiang@chromium.org>
3 files changed