serial: sh-sci: Replace direct stop_rx/stop_tx calls with port ops in sci_shutdown()

Replace direct calls to sci_stop_rx() and sci_stop_tx() with port ops
callbacks in sci_shutdown(). This enables the RSCI driver, which reuses
the SCI core but implements its own stop_rx and stop_tx logic, to reuse
sci_shutdown() without duplicating code.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20250630202323.279809-4-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: prabhakarlad

drivers/tty/serial/sh-sci.c

@@ -2289,8 +2289,8 @@ void sci_shutdown(struct uart_port *port)
 	mctrl_gpio_disable_ms_sync(to_sci_port(port)->gpios);
 
 	uart_port_lock_irqsave(port, &flags);
-	sci_stop_rx(port);
-	sci_stop_tx(port);
+	s->port.ops->stop_rx(port);
+	s->port.ops->stop_tx(port);
 	s->ops->shutdown_complete(port);
 	uart_port_unlock_irqrestore(port, flags);