zipitz2: enable libfdt

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

Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>

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