can: sja1000: sja1000_err(): use error counter for error state

can: sja1000: sja1000_err(): use error counter for error state

The CAN controller sends the EPI interrupt whenever it reaches the error
passive status or enters the error active status from the error passive
status.

Instead of keeping track of the controller status in the driver, read the
txerr and rxerr counters and use can_state_get_by_berr_counter() to
determine the state of the CAN controller.

Suggested-by: Achim Baumgartner <abaumgartner@topcon.com>
Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>
Link: https://patch.msgid.link/20260123-sja1000-state-handling-v2-2-687498087dad@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>