base-files: minor cosmetic corrections for functions.sh

  - update copyright header
  - remove superfluous shebang left-over from changeset 34794
  - unify function declaration

[juhosg: keep Vertical Communications' copyright notice]

Signed-off-by: Michael Heimpold <mhei@heimpold.de>
Signed-off-by: Gabor Juhos <juhosg@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@35646 3c298f89-4303-0410-b956-a3cf2f4a3e73