can: fix return value from can_get_bittiming()

When trying to set a data bitrate on non CAN FD devices the 'ip' tool
answers with:

	RTNETLINK answers: Unknown error 524

Rename '-ENOTSUPP' to '-EOPNOTSUPP' so that 'ip' answers correctly:

       RTNETLINK answers: Operation not supported
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/dev.c

@@ -256,7 +256,7 @@ static int can_get_bittiming(struct net_device *dev, struct can_bittiming *bt,
 
 	/* Check if the CAN device has bit-timing parameters */
 	if (!btc)
-		return -ENOTSUPP;
+		return -EOPNOTSUPP;
 
 	/*
 	 * Depending on the given can_bittiming parameter structure the CAN