scripts: kwboot: shorten delay between two boot messages
Together with the previous changes that allow to handle the scenario where
too many messages were sent, this greatly improves the probability to hit
the time window during which the CPU accepts a boot message.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>