AudioDeviceInfo: make TYPE_REMOTE_SUBMIX public

SUBMIX type can be returned by routing query APIs such as
MediaPlayer.getRoutedDevice(), make it public.

Bug: 160819170
Test: atest AudioHostTest#testTwoChannelCapturingCheckSubmixDevice
Change-Id: Ie5854ad86464c40137d0a1b10420116bc5cc270e
5 files changed