tty: sdio_uart: Fix the locking on "func" for new code

The new dtr_rts function didn't take the port->func lock as it should
so add use of the lock there.
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/mmc/card/sdio_uart.c

@@ -603,10 +603,14 @@ static void uart_dtr_rts(struct tty_port *tport, int onoff)
 {
 	struct sdio_uart_port *port =
 			container_of(tport, struct sdio_uart_port, port);
+	int ret = sdio_uart_claim_func(port);
+	if (ret)
+		return;
 	if (onoff == 0)
 		sdio_uart_clear_mctrl(port, TIOCM_DTR | TIOCM_RTS);
 	else
 		sdio_uart_set_mctrl(port, TIOCM_DTR | TIOCM_RTS);
+	sdio_uart_release_func(port);
 }
 
 /**