Hi,
UEFI needs to be able to network boot on Hikey over ethernet via tftp.
The only option seems to be via USB ethernet dongle. Edk2 even has a driver for AX88772 ethernet dongle (OptionRomPkg/Bus/Usb/UsbNetworking) but it needs to have USB and networking support enabled for HiKey.
Could you add this to your list?
Bill