net: Kconfig: move the CAN device menu to the "Device Drivers" section

The devices are meant to be under the "Device Drivers" category of the
menuconfig. The CAN subsystem is currently one of the rare exception
with all of its devices under the "Networking support" category.

The CAN_DEV menuentry gets moved to fix this discrepancy. The CAN menu
is added just before MCTP in order to be consistent with the current
order under the "Networking support" menu.

A dependency on CAN is added to CAN_DEV so that the CAN devices only
show up if the CAN subsystem is enabled.

Link: https://lore.kernel.org/all/20220610143009.323579-6-mailhol.vincent@wanadoo.fr


Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Acked-by: Max Staudt <max@enpas.org>
Tested-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>