can: Kconfig: convert 'depends on CAN_DEV' into 'if CAN_DEV...endif' block

This patch adds an 'if CAN_DEV...endif' Block around the CAN driver
symbols in drivers/net/can/Kconfig. So the 'depends on CAN' dependencies
can be removed.

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>