Fix dfota support.

Change-Id: I2c3122a67131c525c7f72bda7f1746109bd7a473
diff --git a/mbtk/mbtk_otad/Makefile b/mbtk/mbtk_otad/Makefile
index 28ba357..1ddd589 100755
--- a/mbtk/mbtk_otad/Makefile
+++ b/mbtk/mbtk_otad/Makefile
@@ -13,7 +13,8 @@
 # -Wno-error=unused-function
 CFLAGS +=
 
-DEFINE += -DCONFIG_AB_SYSTEM
+# -DCONFIG_AB_SYSTEM_DFOTA
+DEFINE += -DCONFIG_AB_SYSTEM -DCONFIG_AB_SYSTEM_DFOTA
 
 MY_FILES_PATH:=$(LOCAL_PATH)/src