SurfaceFlinger: fix 64-bit format string warnings

Change-Id: Idacfbf0601743fba1c5de7632201a66a307a2710
Signed-off-by: Greg Hackmann <ghackmann@google.com>
diff --git a/services/surfaceflinger/DisplayDevice.cpp b/services/surfaceflinger/DisplayDevice.cpp
index 1319deb..a1430b9 100644
--- a/services/surfaceflinger/DisplayDevice.cpp
+++ b/services/surfaceflinger/DisplayDevice.cpp
@@ -462,7 +462,7 @@
     result.appendFormat(
         "+ DisplayDevice: %s\n"
         "   type=%x, hwcId=%d, layerStack=%u, (%4dx%4d), ANativeWindow=%p, orient=%2d (type=%08x), "
-        "flips=%u, isSecure=%d, secureVis=%d, acquired=%d, numLayers=%u\n"
+        "flips=%u, isSecure=%d, secureVis=%d, acquired=%d, numLayers=%zu\n"
         "   v:[%d,%d,%d,%d], f:[%d,%d,%d,%d], s:[%d,%d,%d,%d],"
         "transform:[[%0.3f,%0.3f,%0.3f][%0.3f,%0.3f,%0.3f][%0.3f,%0.3f,%0.3f]]\n",
         mDisplayName.string(), mType, mHwcDisplayId,