AAH_RX: Add the ability to control volume and stream type.

DO NOT MERGE

Change the AAH_RX player so that it implements MediaPlayerHWInterface
(instead of just MediaPlayerInterface) so the app level can control
the rendering volume of individual RX player instances as well as the
stream type of the audio tracks created by the RX player.

Change-Id: Ieff1ea774f7981227546744883ee4b4e87a2cd2a
Signed-off-by: John Grossman <johngro@google.com>