floss: Hook AudioState callback

Currently only hook print info log when receiving the AudioState
changes. This needs to be propagated to client to notify the data
socket's readiness in the later CLs.

Tag: #floss
Bug: 213408429
Test: Build, flush and verify the logs on var/log/messages
BYPASS_LONG_LINES_REASON: Bluetooth likes 120 char lines

Change-Id: I80086fa4b78a806b76c2985c23eac436ce877a0e