arm64: zynqmp: Add support for u-boot.itb generation without ATF

If ATF doesn't exist generate u-boot.itb without it and let U-Boot run in
EL3. Still keep warning to let user know that ATF/BL31 is missing.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
1 file changed