serial: 8250: of: Correct of_platform_serial_setup() error handling

Don't dispose IRQ mapping before it has been created.

Fixes: aa9594740 ("serial: 8250_of: Add IO space support")
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@nokia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250_of.c

@@ -124,7 +124,7 @@ static int of_platform_serial_setup(struct platform_device *ofdev,
 				dev_warn(&ofdev->dev, "unsupported reg-io-width (%d)\n",
 					 prop);
 				ret = -EINVAL;
-				goto err_dispose;
+				goto err_unprepare;
 			}
 		}
 		port->flags |= UPF_IOREMAP;