Clean up logging of portId to piid mappings

Since for the mute and format change event only the latest portId is
necessary, now storing for each piid the latest portId change.

Flag: com.android.media.audio.Flags.portToPiidSimplification
Test: adb shell dumpsys audio
Bug: 335747248
Change-Id: Id1c378350c58deaea291997028f5419b3d5bb796