Effect AIDL: Move EffectThread process into mutex

To avoid the case of receive thread stop right before process, in this
case test case AudioEffectTest#ConsumeDataAfterRestart will fail.

Bug: 264618800
Test: atest VtsHalAudioEffectTargetTest
Change-Id: I3c00361a537bc7010e6cd138f637f68b963e8033
4 files changed