Move GenerationCache to the utils directory.

Change-Id: I210ffa8f1d76a102bb7d971c649c20a74d03fbe6
diff --git a/libs/hwui/TextureCache.h b/libs/hwui/TextureCache.h
index 34c5455..467e851 100644
--- a/libs/hwui/TextureCache.h
+++ b/libs/hwui/TextureCache.h
@@ -20,7 +20,7 @@
 #include <SkBitmap.h>
 
 #include "Texture.h"
-#include "GenerationCache.h"
+#include "utils/GenerationCache.h"
 
 namespace android {
 namespace uirenderer {