Rename the Zephyr chosen property for specifying the default CAN bus
controller from "zephyr,can-primary" to "zephyr,canbus".
The "zephyr,can-primary" property name was selected in antipation of
adding support for redundant CAN networks, which we have yet to
add. Meanwhile, the "primary" term causes confusion for non-redundant
CAN bus configurations (and the "can" term doesn't match the name of the
Zephyr CAN bus subsystem).
The CAN in Automation (CiA) 302-6, which deals with CANopen network
redundancy, uses the terms "default interface" and "redundant
interface". If/when we add support for redundant CAN networks, the
"zephyr,canbus" chosen property can be supplemented with a
"zephyr,canbus-redundant" chosen property.
Signed-off-by: Henrik Brix Andersen <hebad@vestas.com>