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/spi/mcp251x.c b/drivers/net/can/spi/mcp251x.c
index c66d699..bf63fee 100644
--- a/drivers/net/can/spi/mcp251x.c
+++ b/drivers/net/can/spi/mcp251x.c
@@ -905,6 +905,7 @@
 		if (priv->can.state == CAN_STATE_BUS_OFF) {
 			if (priv->can.restart_ms == 0) {
 				priv->force_quit = 1;
+				priv->can.can_stats.bus_off++;
 				can_bus_off(net);
 				mcp251x_hw_sleep(spi);
 				break;