Sounds to me (just guessing here) like you hosed u-boot on the SPI NOR chip. You should be able to place u-boot on an sd-card and boot from it. Once in u-boot on the SDcard you should also be able to re-load u-boot on the SPI NOR (assuming this is the issue). I am not sure if they have this process documented yet, but at least writing u-boot to an SDcard should allow you to boot into an operating system.
Hope this helps!
Cheers!
