bluez5: use only one input route
Don't have separate input route for A2DP and HFP, as it is generally not necessary.
When in A2DP mode when there's also HFP possible, emit the input route in SPA_PARAM_Route, even though there is no corresponding input node emitted.
The host may then emit a loopback microphone node, and switch profiles according to its status. Having the input route available at all times allows to retain changes to volume settings made when there is no real input node.