Adding a feature to indicate that the device possesses low-latency audio.

The specific criteria for low-latency audio are defined in the CDD, but since
that hasn't yet been settled for Gingerbread, this change doesn't go into
details. We can do a docs change later once GB CDD is final.

Change-Id: Ic5ad9d04e8ecd78c81b6f09439affec6bf8cb9b2