* Support custom sized SPL/raw boot region
This is required for Rockchip which by default stores the U-Boot FIT
image at the 8MiB offset.
* Ignore shellcheck warning
* Add AArch64/ARM64 EFI boot support (for QEMU and some boards)
* Allow GRUB to load cmdline.txt-like
* Enable qcow2/vmdk disk images
Co-authored-by: Stefan Agner <stefan@agner.ch>