tty: serial: imx: clear the RTSD status before enable the RTSD irq

Clear RTSD status before enabling the irq event for RTSD in
imx_uart_enable_wakeup function.
Since RTSD can be set as the wakeup source, this can avoid any risk of
false triggering of a wake-up interrupts.
Acked-by: NUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: NFugang Duan <fugang.duan@nxp.com>
Signed-off-by: NSherry Sun <sherry.sun@nxp.com>
Link: https://lore.kernel.org/r/20211125014306.4432-1-sherry.sun@nxp.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/imx.c

@@ -2482,10 +2482,12 @@ static void imx_uart_enable_wakeup(struct imx_port *sport, bool on)
 
 	if (sport->have_rtscts) {
 		u32 ucr1 = imx_uart_readl(sport, UCR1);
-		if (on)
+		if (on) {
+			imx_uart_writel(sport, USR1_RTSD, USR1);
 			ucr1 |= UCR1_RTSDEN;
-		else
+		} else {
 			ucr1 &= ~UCR1_RTSDEN;
+		}
 		imx_uart_writel(sport, ucr1, UCR1);
 	}
 }