libhardware_legacy: Add support for DirectTrack

-Add new APIs to AudioStreamOut class.
-Add audio output flags to openOutputStream.

Change-Id: Idcbca5d8ea3bd3f7ea008e42ae685f3f1b24dc6c
(cherry picked from commit c2238e581c815dbf33625011ad32a97067d1ab52)
(cherry picked from commit 87d4ab5eee4124403012cb3e5440d36eb0df9586)