tty: serial: xilinx_uartps: Supply description for missing member 'cts_override'

Fixes the following W=1 kernel build warning(s):

 drivers/tty/serial/xilinx_uartps.c:205: warning: Function parameter or member 'cts_override' not described in 'cdns_uart'

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: Michal Simek <michal.simek@xilinx.com>
Cc: linux-serial@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20201104193549.4026187-23-lee.jones@linaro.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/xilinx_uartps.c

@@ -192,6 +192,7 @@ MODULE_PARM_DESC(rx_timeout, "Rx timeout, 1-255");
  * @baud:		Current baud rate
  * @clk_rate_change_nb:	Notifier block for clock changes
  * @quirks:		Flags for RXBS support.
+ * @cts_override:	Modem control state override
  */
 struct cdns_uart {
 	struct uart_port	*port;