dejagnu: needs expect at runtime

runtest return an error due to missing expect on the target.
Add expect as runtime dependency.

Signed-off-by: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit d9a3a08e)
Signed-off-by: Steve Sakoman <steve@sakoman.com>