MidiService: clear status when device unbound

This can help prevent MIDI input ports from getting
stuck in the open position.

Bug: 210724686
Test: see bug for repro steps
Test: atest CtsMidiTestCases
Test: https://source.android.com/devices/audio/midi_test.html
Test: Check status with:  adb shell dumpsys midi
Change-Id: I9fe45eeb2d51356d114ae5a1a175e3d1f6977328