Hmmm, well that's not positive. With the kernel not starting at all there are no clues where to go next.
Perhaps extract all the mtds from the flash via uboot and see if there's a working fdt in there (maybe not as it doesn't boot + appears the developers were booting from usb).
And try the images mentioned above for ap3825i and go through the steps used in that thread to bring the device up.
Images here;
https://downloads.laboratoryb.org/releases/snapshot/targets/mpc85xx/p1020/