can: move can_stats.bus_off++ from can_bus_off into can_change_state

In order to be able to move the stats increment from can_bus_off() into
can_change_state(), the increment had to be moved back into code that was using
can_bus_off() but not can_change_state().

As a side-effect, this patch fixes the following bugs:
 * Redundant call to can_bus_off() in c_can.
 * Bus-off counted twice in xilinx_can.

Signed-off-by: Andri Yngvason <andri.yngvason@marel.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
diff --git a/drivers/net/can/pch_can.c b/drivers/net/can/pch_can.c
index a67eb01..e187ca7 100644
--- a/drivers/net/can/pch_can.c
+++ b/drivers/net/can/pch_can.c
@@ -505,6 +505,7 @@
 		pch_can_set_rx_all(priv, 0);
 		state = CAN_STATE_BUS_OFF;
 		cf->can_id |= CAN_ERR_BUSOFF;
+		priv->can.can_stats.bus_off++;
 		can_bus_off(ndev);
 	}