can: slcan: slcan_init() convert printk(LEVEL ...) to pr_level()

Convert the last printk(LEVEL ...) to pr_level().

Link: https://lore.kernel.org/all/20220704125954.1587880-3-mkl@pengutronix.deSigned-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/slcan/slcan-core.c

@@ -1057,7 +1057,7 @@ static int __init slcan_init(void)
 	/* Fill in our line protocol discipline, and register it */
 	status = tty_register_ldisc(&slc_ldisc);
 	if (status)  {
-		printk(KERN_ERR "slcan: can't register line discipline\n");
+		pr_err("slcan: can't register line discipline\n");
 		kfree(slcan_devs);
 	}
 	return status;