audio: Reconfigure backend based on stream's capability

If a stream configuration (bit width, rate, channel count)
is a better match for the sink (e.g. USB) than the existing
configuration, do a force routing to match the better
configuration.

Test: test music/video/ringtone playback, camcorder, OK google capture,
voice call

Change-Id: I5a7c4c4350518e53829c01757f4dc7fed54f3eca