Revert^4 "Reapply "AudioFlinger: Control volume using Port ID""

This reverts commit 2e077f0fb2478163c82ca15b18b0fa67fabcb217.

Reason for revert: forward fix will be applied

Change-Id: I82f8e29c788e6b1be59e81f127472f7cd36cd126
diff --git a/services/audioflinger/TrackBase.h b/services/audioflinger/TrackBase.h
index a0b85f7..1342b7b 100644
--- a/services/audioflinger/TrackBase.h
+++ b/services/audioflinger/TrackBase.h
@@ -347,7 +347,7 @@
     size_t              mBufferSize; // size of mBuffer in bytes
     // we don't really need a lock for these
     MirroredVariable<track_state>  mState;
-    const audio_attributes_t mAttr;
+    audio_attributes_t  mAttr;
     const uint32_t      mSampleRate;    // initial sample rate only; for tracks which
                         // support dynamic rates, the current value is in control block
     const audio_format_t mFormat;