[D18][ENV] fix load address variables
Move forward by 0x01000000 (16MiB) the load addresses subsequent to the
kernel load address: this fixes the error FDT image overlaps OS image
that occurred on adding new built-in drivers to kernel defconfig.
Also shrink to 0x00100000 (1MiB) the seco config tool offset between
FDT overlay, as it is more than enough.