can: remove useless defaults in Kconfig

There's no need for "default N' (or 'default n') as it's default.

Signed-off-by: Kurt Van Dijck <kurt.van.dijck@eia.be>
Acked-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>