serial: 8250: Unlink uart console ptr if console setup fails

If console setup fails (eg., there is no valid port at that index),
unlink the console ptr; otherwise, when the driver unloads, the
console will be unregistered (even though setup, and thus registration,
failed) and a console disabled message will be printed.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250_core.c

@@ -597,6 +597,7 @@ static void univ8250_console_write(struct console *co, const char *s,
 static int univ8250_console_setup(struct console *co, char *options)
 {
 	struct uart_port *port;
+	int retval;
 
 	/*
 	 * Check whether an invalid uart number has been specified, and
@@ -609,7 +610,10 @@ static int univ8250_console_setup(struct console *co, char *options)
 	/* link port to console */
 	port->cons = co;
 
-	return serial8250_console_setup(port, options, false);
+	retval = serial8250_console_setup(port, options, false);
+	if (retval != 0)
+		port->cons = NULL;
+	return retval;
 }
 
 /**