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/usb/ems_usb.c b/drivers/net/can/usb/ems_usb.c
index 29d3f09..9376f5e 100644
--- a/drivers/net/can/usb/ems_usb.c
+++ b/drivers/net/can/usb/ems_usb.c
@@ -347,6 +347,7 @@
 			dev->can.state = CAN_STATE_BUS_OFF;
 			cf->can_id |= CAN_ERR_BUSOFF;
 
+			dev->can.can_stats.bus_off++;
 			can_bus_off(dev->netdev);
 		} else if (state & SJA1000_SR_ES) {
 			dev->can.state = CAN_STATE_ERROR_WARNING;