When passing unhandled arguments as in

  % barebox-state foo

these will be silently ignored. This may lead to misunderstandings and
unintended behavior, thus the user should be informed and the programm
should exit with an error in these cases.

Signed-off-by: Enrico Jorns <ejo@pengutronix.de>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>