serial: liteuart: Fix NULL pointer dereference in ->remove()

drvdata has to be set in _probe() - otherwise platform_get_drvdata()
causes null pointer dereference BUG in _remove().

Fixes: 1da81e55 ("drivers/tty/serial: add LiteUART driver")
Cc: stable <stable@vger.kernel.org>
Reviewed-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Ilia Sergachev <silia@ethz.ch>
Link: https://lore.kernel.org/r/20211115224944.23f8c12b@dtkwSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/liteuart.c

@@ -285,6 +285,8 @@ static int liteuart_probe(struct platform_device *pdev)
 	port->line = dev_id;
 	spin_lock_init(&port->lock);
 
+	platform_set_drvdata(pdev, port);
+
 	return uart_add_one_port(&liteuart_driver, &uart->port);
 }