This patch fixes the behaviour to not overwrite csma settings when
set channel afterwards.

Cc: Stefan Schmidt <stefan@osg.samsung.com>
Acked-by: NStefan Schmidt <stefan@osg.samsung.com>
Signed-off-by: NAlexander Aring <aar@pengutronix.de>
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>