When the USB device is unplugged, gs_can_close() (which implements the
struct net_device_ops::ndo_stop callback) is called. In this function
an attempt is made to shut down the USB device with a USB control
message. For disconnected devices this will fail and a warning message
is printed.

Silence the driver by removing the printout of the error message if
the reset command fails.

Link: https://lore.kernel.org/all/20230718-gs_usb-cleanups-v1-9-c3b9154ec605@pengutronix.deSigned-off-by: Marc Kleine-Budde <mkl@pengutronix.de>