Fix underrun count for static tracks

Should always return 0 - static tracks don't underrun.

Test: Soundpool with 40+ static tracks and enabling Bluetooth
Bug: 73550407
Change-Id: I1e31970eb88a21ce06fc3e0383f4e4b969ad9f02

include/private/media/AudioTrackShared.h

@@ -438,7 +438,11 @@ public:
         return 0;
     }
 
-    virtual uint32_t    getUnderrunFrames() const {
+    virtual uint32_t getUnderrunFrames() const override {
+        return 0;
+    }
+
+    virtual uint32_t getUnderrunCount() const override {
         return 0;
     }