SoundPool: Clean up Stream::play_l logic for garbage collection

Test: soundpool_stress
Test: atest SoundPoolAacTest
Test: atest SoundPoolHapticTest
Test: atest SoundPoolMidiTest
Test: atest SoundPoolOggTest
Bug: 210682934
Change-Id: Ief7ff8415861570c0f2f817bfae7e88948d810c0
1 file changed