To boot FreeBSD kernel from the onboard flash on an AVILA board:

load your kernel, in binary form, with

load -r -b 0x00200000 kernel.bin (or kernel.gz.tramp.bin, as produced by
"make trampoline", if you want to use a gzipped kernel).
The first time, you'll have to remove linux from the flash, with the following
commands:
fis delete zimage
fis delete ramdisk
Then you can flash the FreeBSD kernel with the following command :
fis create -b 0x00200000 -f 0x50080000 -l 0x400000 kernel
The -l flag gives the length, so your mileage may vary.
Then you can jump to the kernel just by using go 0x50080000

To update the kernel, you do the same except that instead of deleting linux,
you delete the previous kernel image by using
fis delete kernel 
(this part is optional if your kernel has the same size as the previous one)