can: kvaser_usb: fix return value for hif_usb_send_regout

As the potential failure of usb_submit_urb(), it should be better to
return the err variable to catch the error.

Signed-off-by: Chen Ni <nichen@iscas.ac.cn>
Link: https://lore.kernel.org/all/20240521041020.1519416-1-nichen@iscas.ac.cn
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>