serial: sh-sci: Always set TIOCM_CTS in .get_mctrl() callback

Documentation/serial/driver clearly states:

    If the port does not support CTS, DCD or DSR, the driver should
    indicate that the signal is permanently active.

Hence always set TIOCM_CTS, as we currently don't look at the CTS
hardware line state at all.

FWIW, this fixes the transmit path when hardware-assisted flow control
is enabled, and userspace enables CRTSCTS.
The receive path is still broken, as RTS is never asserted.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/sh-sci.c

@@ -1835,9 +1835,9 @@ static unsigned int sci_get_mctrl(struct uart_port *port)
 {
 	/*
 	 * CTS/RTS is handled in hardware when supported, while nothing
-	 * else is wired up. Keep it simple and simply assert DSR/CAR.
+	 * else is wired up. Keep it simple and simply assert CTS/DSR/CAR.
 	 */
-	return TIOCM_DSR | TIOCM_CAR;
+	return TIOCM_CTS | TIOCM_DSR | TIOCM_CAR;
 }
 
 static void sci_break_ctl(struct uart_port *port, int break_state)