Device and mode definitions for remote submix

A remote submix is an audio mix of audio streams that
 are not going to be played directly through the platform mix,
 but rather will be mixed together to be handled in a
 different manner. This mix can be obtained by recording
 it through the AUDIO_IN_REMOTE_SUBMIX and presenting it
 remotely (as opposed to local playback == on the device
 itself).

All changes marked "temporary" will be overriden by the
 changes to update the audio device definitions for
 the 2.0 API.

Change-Id: I9c6da607fc50b7b8545d189ac5b083107369cfb5