Start using unodified Developer Certificate of Origin v1.1

Start using unodified Developer Certificate of Origin v1.1

With the license terms having been cleaned up in the hostap.git files,
there is no continued need for the additional (e) item to explicitly
acknowledge BSD license option for contributions. Since DCO v1.1 is now
available from http://developercertificate.org/ it looks reasonable to
move to the unmodified version of DCO and to the commonly used
Signed-off-by tag for this project.

Signed-hostap: Jouni Malinen <j@w1.fi>
Signed-off-by: Jouni Malinen <j@w1.fi>