serial: 8250_lpss: Enable PSE UART Auto Flow Control

Add a call to the custom ->set_termios() which has implementation about
changing the state of RTS and CTS.

Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Signed-off-by: Aman Kumar <aman.kumar@intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20211005133026.21488-2-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250_lpss.c

@@ -164,6 +164,9 @@ static int ehl_serial_setup(struct lpss8250 *lpss, struct uart_port *port)
 	 * matching with the registered General Purpose DMA controllers.
 	 */
 	up->dma = dma;
+
+	port->set_termios = dw8250_do_set_termios;
+
 	return 0;
 }