can: mcba_usb: fix use-after-free on disconnect

The driver was accessing its driver data after having freed it.

Fixes: 51f3baad7de9 ("can: mcba_usb: Add support for Microchip CAN BUS Analyzer")
Cc: stable <[e-mail]> # 4.12
Cc: Remigiusz Kołłątaj <[e-mail]>
Reported-by: [e-mail]
Signed-off-by: Johan Hovold <[e-mail]>
Signed-off-by: Marc Kleine-Budde <[e-mail]>

drivers/net/can/usb/mcba_usb.c

···
 	netdev_info(priv->netdev, "device disconnected\n");
 
 	unregister_candev(priv->netdev);
-	free_candev(priv->netdev);
-
 	mcba_urb_unlink(priv);
+	free_candev(priv->netdev);
 }
 
 static struct usb_driver mcba_usb_driver = {