chromeos/audio: Add hychao@ to OWNERS.

BUG=None
TEST=None

Change-Id: I4c7cf261450016822c6f2b5f3fbef3445dfd9a69
Reviewed-on: https://chromium-review.googlesource.com/618529Reviewed-by: Jenny Zhang <jennyz@chromium.org>
Commit-Queue: Wu-Cheng Li <wuchengli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#496604}

chromeos/audio/OWNERS

 jennyz@chromium.org
+hychao@chromium.org