Put together a new version of u-boot for installation in SPI. Checked on their models work. To install put together a special script (s905_autoscript), which allows you to install a new version of u-boot in SPI without using the UART. Please note that this test version, you need to be prepared for possible bugs.
Pay attention with the new boot loader in SPI can only work as long as the firmware is specifically designed for such work (Server_20171025)