Some devices have a U-boot variant that does not accept a third
parameter on the "bootm" command, meaning we can't override the dtb
in the bootloader so have to smush it back into the kernel image
This doesn't work in QEMU but I think the problem is with the
U-Boot configuration for QEMU. It does work on at least one
hardware device so I'm pushing it anyway
Based on
https://gti.telent.net/raboof/liminix/src/branch/tftp-old-uboot
Co-authored-by: Arnout Engelen <arnout@bzzt.net>