aaudio: rename timestamp variables

There were several different timestamp variables with slightly
different meaning but with the same name.
That made it hard to debug the code.

Test: atest CtsNativeMediaAAudioTestCases
Change-Id: Iebf438676925c698377abe02c81f3d559829318a
diff --git a/services/oboeservice/AAudioServiceStreamBase.h b/services/oboeservice/AAudioServiceStreamBase.h
index 7904b25..ffc768b 100644
--- a/services/oboeservice/AAudioServiceStreamBase.h
+++ b/services/oboeservice/AAudioServiceStreamBase.h
@@ -301,7 +301,7 @@
     // TODO rename mClientHandle to mPortHandle to be more consistent with AudioFlinger.
     audio_port_handle_t     mClientHandle = AUDIO_PORT_HANDLE_NONE;
 
-    SimpleDoubleBuffer<Timestamp>  mAtomicTimestamp;
+    SimpleDoubleBuffer<Timestamp>  mAtomicStreamTimestamp;
 
     android::AAudioService &mAudioService;