Update audio comments

Change-Id: I85d7d2f6381b251db5695202fec75128883a8662
diff --git a/include/private/media/AudioTrackShared.h b/include/private/media/AudioTrackShared.h
index 3063448..bbc5e26 100644
--- a/include/private/media/AudioTrackShared.h
+++ b/include/private/media/AudioTrackShared.h
@@ -54,9 +54,10 @@
                 uint32_t    serverBase;
 
                 int         mPad1;          // unused, but preserves cache line alignment
+
                 uint32_t    frameCount;
 
-                // Cache line boundary
+                // Cache line boundary (32 bytes)
 
                 uint32_t    loopStart;
                 uint32_t    loopEnd;        // read-only for server, read/write for client