can: gs_usb: gs_can_open(): prevent memory leak

In gs_can_open() if usb_submit_urb() fails the allocated urb should be
released.

Fixes: d08e973a77d1 ("can: gs_usb: Added support for the GS_USB CAN devices")
Cc: linux-stable <[e-mail]>
Signed-off-by: Navid Emamdoost <[e-mail]>
Signed-off-by: Marc Kleine-Budde <[e-mail]>

drivers/net/can/usb/gs_usb.c

···
 					   rc);
 
 				usb_unanchor_urb(urb);
+				usb_free_urb(urb);
 				break;
 			}