CRAS: dbus - Add SetAudioSuspend method

Add SetAudioSuspend method which will be used by
power_manager to turn on/off system audio at suspend
and resume.

BUG=chromium:463756
TEST=dbus-send --system  --type=method_call --print-reply
--dest=org.chromium.cras /org/chromium/cras
org.chromium.cras.Control.SetSuspendAudio boolean:true

Change-Id: Ied491756b7ae380cef8b7e84e28d408a2c34f180
Reviewed-on: https://chromium-review.googlesource.com/257989
Reviewed-by: Dylan Reid <dgreid@chromium.org>
Commit-Queue: Hsinyu Chao <hychao@chromium.org>
Tested-by: Hsinyu Chao <hychao@chromium.org>
6 files changed