can: ucan: ucan_disconnect(): change unregister_netdev() to unregister_candev()

From API pairing, change unregister_netdev() to unregister_candev()
since the registration function is register_candev(). Actually, they
are the same.

Signed-off-by: Dongliang Mu <dzm91@hust.edu.cn>
Link: https://lore.kernel.org/all/20221024110033.727542-1-dzm91@hust.edu.cn


[mkl: adjust subject + commit message]
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>