audioflinger: volume control to HAL for VoIP streams

Do not apply stream volume in software for special VoIP output
stream mixers but send it to the HAL instead.

Bug: 64392515.
Test: Fi calls
Change-Id: I698a1a0ad17d672d09187529dcbc5d259284e4af
diff --git a/services/audioflinger/Threads.h b/services/audioflinger/Threads.h
index 8d7bb1a..dd2b89b 100644
--- a/services/audioflinger/Threads.h
+++ b/services/audioflinger/Threads.h
@@ -999,6 +999,9 @@
                 bool        mHwSupportsPause;
                 bool        mHwPaused;
                 bool        mFlushPending;
+                // volumes last sent to audio HAL with stream->setVolume()
+                float mLeftVolFloat;
+                float mRightVolFloat;
 };
 
 class MixerThread : public PlaybackThread {
@@ -1116,9 +1119,6 @@
 
     virtual     void        onAddNewTrack_l();
 
-    // volumes last sent to audio HAL with stream->set_volume()
-    float mLeftVolFloat;
-    float mRightVolFloat;
     bool mVolumeShaperActive;
 
     DirectOutputThread(const sp<AudioFlinger>& audioFlinger, AudioStreamOut* output,