SurfaceFlinger: fix 64-bit format string warnings

Change-Id: Idacfbf0601743fba1c5de7632201a66a307a2710
Signed-off-by: Greg Hackmann <ghackmann@google.com>
diff --git a/services/surfaceflinger/EventThread.cpp b/services/surfaceflinger/EventThread.cpp
index 3528b62..d868f32 100644
--- a/services/surfaceflinger/EventThread.cpp
+++ b/services/surfaceflinger/EventThread.cpp
@@ -328,7 +328,7 @@
             mDebugVsyncEnabled?"enabled":"disabled");
     result.appendFormat("  soft-vsync: %s\n",
             mUseSoftwareVSync?"enabled":"disabled");
-    result.appendFormat("  numListeners=%u,\n  events-delivered: %u\n",
+    result.appendFormat("  numListeners=%zu,\n  events-delivered: %u\n",
             mDisplayEventConnections.size(),
             mVSyncEvent[DisplayDevice::DISPLAY_PRIMARY].vsync.count);
     for (size_t i=0 ; i<mDisplayEventConnections.size() ; i++) {