Correct some broken printf() like format mismatches

Fix two places where a printf()-style format string does not match the
arguments passed.

Reported-by: Nicolas Iooss <[email protected]>
Signed-off-by: David Gibson <[email protected]>
diff --git a/util.h b/util.h
index f5c4f1b..35b2bda 100644
--- a/util.h
+++ b/util.h
@@ -53,7 +53,7 @@
 	void *new = realloc(p, len);
 
 	if (!new)
-		die("realloc() failed (len=%d)\n", len);
+		die("realloc() failed (len=%zd)\n", len);
 
 	return new;
 }