base-files: create /etc/config/ directory

base-files: create /etc/config/ directory

The /bin/config_generate script and some other scripts are assuming the
/etc/config directory exists in the image. This is true in case for
example the package firewall, dropbear or dnsmasq are included, which
are adding the files under /etc/config/. Without any of these package
the system will not boot up fully because the /etc/config/ directory is
missing and some init scripts just fail.

Make sure all images with the base-files contain a /etc/config/
directory.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Acked-by: John Crispin <john@phrozen.org>