Move syslinux to chromiumos-overlay

We're looking to bring back the "quieter" boot behavior, so we're
pulling this back into the overlay.

BUG=b:179809020
TEST=`cros_sdk$ sudo emerge sys-boot/syslinux && ./build_image;
      latest$ qemu-system-x86_64 -vga virtio -display sdl,gl=on \
          -drive format=raw,file=chromiumos_image.bin`:
     confirm syslinux banner, and that the splashscreen comes up

Cq-Depend: chromium:2745581
Change-Id: I3db366552a79fcc8f5d92a1a09be70cdf17684a2
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/portage-stable/+/2745877
Tested-by: Ted Brandston <tbrandston@google.com>
Commit-Queue: Ted Brandston <tbrandston@google.com>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
6 files changed