iMX6 Sabre board: Ubuntu 16.04 build & kernal module issue

I am using Imx6Q sabre-sd board bought from DigiKey.So far, I only install SPL and u-boot.img to SD card follow the instructions but it has no message output in serial console.

I wonder something or step is missing, do you have prebuilt u-boot image and related files? I'd like to try it. Thanks!