scripts/dtc: add fdt_overlay.c and fdt_addresses.c to sync script

libfdt has gained some new files. We need to include them in the
kernel's copy.

Reported-by: Kyle Yan <kyan@codeaurora.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Atman <masteratman@gmail.com>