arm: aarch64: Copy the generic aarch64 RPi U-Boot over too
    
    Set up the generic aarch64 Raspberry Pi U-Boot so that we can
    boot any new device that we may not have specific support for.
    We'll use this method to support the new Zero 2 W.
    
    Signed-off-by: Peter Robinson <pbrobinson@fedoraproject.org>