hammerhead: Enable USB audio

Change-Id: I83861e0c70eeeb5035f89bfa4c32f19c21236437
hammerhead: Always keep 3 buffers ready

 * Reduces overall jank system-wide

Change-Id: I37f6021237c81197063d3fd1fd7e5e07626490c9
hammerhead: Better mount options to improve performance

Change-Id: I18f7165c2ff8547b7968d946336d948fe30522b1
hammerhead: Enable offload for USB audio

Change-Id: I7cc9580865da63330a0bf54d5716ca23a2d6216c