zipitz2: enable libfdt

zipitz2 supports DT boot since linux-4.4 (not mainlined yet)

Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>
diff --git a/include/configs/zipitz2.h b/include/configs/zipitz2.h
index 169eaf3..f69b52e 100644
--- a/include/configs/zipitz2.h
+++ b/include/configs/zipitz2.h
@@ -47,6 +47,7 @@
 #define	CONFIG_SETUP_MEMORY_TAGS
 #define	CONFIG_SYS_TEXT_BASE		0x0
 #define	CONFIG_LZMA			/* LZMA compression support */
+#define	CONFIG_OF_LIBFDT
 
 /*
  * Serial Console Configuration