serial: samsung: Fix unintended usage of uart port 0 as console

In s3c24xx_serial_console_setup function, if the uart port that is
being setup as a console has not been initialized, an error can be
returned instead of using uart port 0 as the default console port.
The uart port that was intended to be used as a console could be
initialized at a later point during boot and then registered as a
console. This will avoid using uart port 0 as a unintended console
port.
Signed-off-by: NThomas Abraham <thomas.ab@samsung.com>
Signed-off-by: NKukjin Kim <kgene.kim@samsung.com>

drivers/tty/serial/samsung.c

@@ -1416,10 +1416,8 @@ s3c24xx_serial_console_setup(struct console *co, char *options)
 
 	/* is the port configured? */
 
-	if (port->mapbase == 0x0) {
-		co->index = 0;
-		port = &s3c24xx_serial_ports[co->index].port;
-	}
+	if (port->mapbase == 0x0)
+		return -ENODEV;
 
 	cons_uart = port;