libfdt: move CONFIG_OF_LIBFDT and CONFIG_FIT to lib/Makefile

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/lib/Makefile b/lib/Makefile
index e8635ef..3ceb697 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -13,7 +13,8 @@
 obj-$(CONFIG_ZLIB) += zlib/
 obj-$(CONFIG_BZIP2) += bzip2/
 obj-$(CONFIG_TIZEN) += tizen/
-obj-y += libfdt/
+obj-$(CONFIG_OF_LIBFDT) += libfdt/
+obj-$(CONFIG_FIT) += libfdt/
 
 obj-$(CONFIG_AES) += aes.o
 obj-$(CONFIG_USB_TTY) += circbuf.o