Cast buffer width and height to int

GraphicBuffer::get{Width,Height} are going to start returning uint32_t
values soon, so add the cast now to avoid breaking the build later.

Change-Id: Ied33700fdf81e8aecbad95d66583818d15987b93
diff --git a/libs/hwui/DeferredLayerUpdater.cpp b/libs/hwui/DeferredLayerUpdater.cpp
index d02455c..16d61fd 100644
--- a/libs/hwui/DeferredLayerUpdater.cpp
+++ b/libs/hwui/DeferredLayerUpdater.cpp
@@ -97,8 +97,8 @@
         sp<GraphicBuffer> buffer = mSurfaceTexture->getCurrentBuffer();
         if (buffer != NULL) {
             // force filtration if buffer size != layer size
-            forceFilter = mWidth != buffer->getWidth()
-                    || mHeight != buffer->getHeight();
+            forceFilter = mWidth != static_cast<int>(buffer->getWidth())
+                    || mHeight != static_cast<int>(buffer->getHeight());
         }
 
         #if DEBUG_RENDERER