base

AudioService: Migrate index map to SparseIntArray.

 - Use SparseIntArray instead of a generic hash map.
 - Avoids unnecessary boxing/unboxing.
 - Avoids unnecessary allocation for iterator temp objects.
 - Provides deterministic dumping (by ascending device order).

Change-Id: If5ca5edd94af90cfed65ecbbbc1f4929f50ab6e9