SECO JUNO (SBC-D23): Add mainline Trusted Firmware-A image to bootloader firmware
Currently trust.img, used in the boot flow, is packaged from Rockchip binaries.
Add support to build trusted-firmware-a (bl31.bin) and to package it along with u-boot-nodtb.bin, u-boot.dtb into one FIT image - u-boot.itb.
https://git.trustedfirmware.org/TF-A/trusted-firmware-a.git/about/
https://opensource.rock-chips.com/wiki_Boot_option
This issue to be completed first: #842