can: peak_usb: replace unregister_netdev() with unregister_candev()

This patch changes the call to unregister_netdev() in
peak_usb_disconnect() with unregister_candev().

Signed-off-by: Stephane Grosjean <s.grosjean@peak-system.com>
Signed-off-by: Lukas Magel <lukas.magel@posteo.net>
Link: https://lore.kernel.org/all/20230116200932.157769-5-lukas.magel@posteo.net
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>