mac802154: remove const for non pointer in rdev-ops

This patches removes the const keyword in variables which are non
pointers. There is no sense to declare call by value parameters as
const.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Reported-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>