Remove unnecessary "out of memory" message from the error path of
gs_can_start_xmit() and gs_can_open().

Convert the printout in case of a failing usb_submit_urb() in
gs_can_open() from numbers to human readable error codes.

Link: https://lore.kernel.org/all/20230718-gs_usb-cleanups-v1-8-c3b9154ec605@pengutronix.deSigned-off-by: Marc Kleine-Budde <mkl@pengutronix.de>