ext4_utils: Fix warnings

Change-Id: Ibeb2001a1ac8cfedd9fced11b17afba4940b6bd5
diff --git a/ext4_utils/make_ext4fs.c b/ext4_utils/make_ext4fs.c
index 2160d56..3fee133 100644
--- a/ext4_utils/make_ext4fs.c
+++ b/ext4_utils/make_ext4fs.c
@@ -20,6 +20,7 @@
 #include "allocate.h"
 #include "contents.h"
 #include "uuid.h"
+#include "backed_block.h"
 
 #include <dirent.h>
 #include <libgen.h>