serial: uartps: Enable automatic flow control

Enable automatic flow control which should ensure that there is no
mainteinance in connection for zcu100 BT case.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Acked-by: Nava kishore Manne <navam@xilinx.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/xilinx_uartps.c

@@ -1006,13 +1006,12 @@ static void cdns_uart_set_mctrl(struct uart_port *port, unsigned int mctrl)
 	val = readl(port->membase + CDNS_UART_MODEMCR);
 	mode_reg = readl(port->membase + CDNS_UART_MR);
 
-	val &= ~(CDNS_UART_MODEMCR_RTS | CDNS_UART_MODEMCR_DTR);
+	val &= ~(CDNS_UART_MODEMCR_RTS | CDNS_UART_MODEMCR_DTR |
+		 CDNS_UART_MODEMCR_FCM);
 	mode_reg &= ~CDNS_UART_MR_CHMODE_MASK;
 
-	if (mctrl & TIOCM_RTS)
-		val |= CDNS_UART_MODEMCR_RTS;
-	if (mctrl & TIOCM_DTR)
-		val |= CDNS_UART_MODEMCR_DTR;
+	if (mctrl & TIOCM_RTS || mctrl & TIOCM_DTR)
+		val |= CDNS_UART_MODEMCR_FCM;
 	if (mctrl & TIOCM_LOOP)
 		mode_reg |= CDNS_UART_MR_CHMODE_L_LOOP;
 	else