USB: serial: xr: avoid requesting zero DTE rate

When the requested line speed is B0 (hangup) there is no need to use the
current speed in the line-coding request. This specifically avoids
requesting a zero DTE rate when the current speed is B0, which could
potentially confuse buggy firmware.
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>

drivers/usb/serial/xr_serial.c

@@ -749,8 +749,6 @@ static void xr_cdc_set_line_coding(struct tty_struct *tty,
 
 	if (tty->termios.c_ospeed)
 		lc->dwDTERate = cpu_to_le32(tty->termios.c_ospeed);
-	else if (old_termios)
-		lc->dwDTERate = cpu_to_le32(old_termios->c_ospeed);
 	else
 		lc->dwDTERate = cpu_to_le32(9600);