Use uint32_t for sample rate

Change-Id: Ie240b48fb54b08359f69ecd4e5f8bda3d15cbe80
diff --git a/include/media/IAudioFlinger.h b/include/media/IAudioFlinger.h
index 0aa48c6..5fd5044 100644
--- a/include/media/IAudioFlinger.h
+++ b/include/media/IAudioFlinger.h
@@ -192,7 +192,7 @@
     // helpers for android.media.AudioManager.getProperty(), see description there for meaning
     // FIXME move these APIs to AudioPolicy to permit a more accurate implementation
     // that looks on primary device for a stream with fast flag, primary flag, or first one.
-    virtual int32_t getPrimaryOutputSamplingRate() = 0;
+    virtual uint32_t getPrimaryOutputSamplingRate() = 0;
     virtual int32_t getPrimaryOutputFrameCount() = 0;
 
 };