audio: Use more bursts in audio I/O VTS tests

Some audio outputs use A/V sync and requre mode bursts
in order to start reporting the presentation position.

Bug: 300735639
Bug: 328010709
Test: atest VtsHalAudioCoreTargetTest
Change-Id: Icad0942f2ba1dcd6f030a7dc4f37e22fdbd6dd71