lib: json: Silence warning about unused parameter

Signed-off-by: Leandro Pereira <leandro.pereira@intel.com>
diff --git a/lib/json/json.c b/lib/json/json.c
index 576e55f..2d9f01b 100644
--- a/lib/json/json.c
+++ b/lib/json/json.c
@@ -903,6 +903,8 @@
 
 	*total += (ssize_t)len;
 
+	ARG_UNUSED(bytes);
+
 	return 0;
 }