can: gs_usb: gs_usb_receive_bulk_callback(): make use of netdev

Make use the previously assigned variable netdev instead of using
dev->netdev.

Link: https://lore.kernel.org/all/20230718-gs_usb-cleanups-v1-5-c3b9154ec605@pengutronix.de


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