Adds getPort (hidden) to AudioDeviceInfo class

Motivation of this change:

In CarAudioService, we enumerate the AudioDeviceInfo on device via
AudioManager.getDevices(). The AudioDeviceInfo would be used to
construct the dynamic routing via AudioMix.Builder, which accepts
AudioDeviceInfo.

Meanwhile, we wire also the volume change to hal via
AudioManager.setAudioPortConfig(), which accepts AudioPort.

Bug: 65751827
Test: lunch bat_land-userdebug && m -j
Change-Id: I438cfd61e502340def5376fe373a296ab69ff86e