Add a defconfig to build an AArch64 disk image with a U-Boot based firmware implementing the subset of UEFI defined by EBBR[1], as well as a Linux OS booting with UEFI, to run on the ROCKPro64 from Pine64. The generated firmware binary can also be used to install or run another OS supporting the EBBR specification. [1] https://github.com/ARM-software/ebbr Signed-off-by: Vincent Stehlé <vincent.stehle@arm.com> Cc: Giulio Benetti <giulio.benetti@benettiengineering.com> Cc: Jagan Teki <jagan@amarulasolutions.com> Cc: Suniel Mahesh <sunil@amarulasolutions.com> Signed-off-by: Julien Olivain <ju.o@free.fr>