can: at91_can: at91_irq_err_line(): send error counters with state change

can: at91_can: at91_irq_err_line(): send error counters with state change

Since 3e5c291c7942 ("can: add CAN_ERR_CNT flag to notify availability
of error counter") there is a dedicated flag to inform the user space,
that there are CAN error counters in the CAN error frame.

In case the device is not in bus off mode, send the error counters to
user space and set CAN_ERR_CNT.

Link: https://lore.kernel.org/all/20231005-at91_can-rx_offload-v2-25-9987d53600e0@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>