can: kvaser_usb_leaf: Fix wrong CAN state after stopping

0bfd:0124 Kvaser Mini PCI Express 2xHS FW 4.18.778 sends a
CMD_CHIP_STATE_EVENT indicating bus-off after stopping the device,
causing a stopped device to appear as CAN_STATE_BUS_OFF instead of
CAN_STATE_STOPPED.

Fix that by not handling error events on stopped devices.

Fixes: 080f40a6 ("can: kvaser_usb: Add support for Kvaser CAN/USB devices")
Tested-by: Jimmy Assarsson <extja@kvaser.com>
Signed-off-by: Anssi Hannula <anssi.hannula@bitwise.fi>
Signed-off-by: Jimmy Assarsson <extja@kvaser.com>
Link: https://lore.kernel.org/all/20221010185237.319219-8-extja@kvaser.com


Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>