USB: ftdi_sio: remove tty->low_latency

Fixes tty_flip_buffer_push being called from hard interrupt context with
low_latency set.
Signed-off-by: NJohan Hovold <jhovold@gmail.com>
Cc: stable <stable@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/usb/serial/ftdi_sio.c

@@ -1234,7 +1234,6 @@ static int set_serial_info(struct tty_struct *tty,
 					(new_serial.flags & ASYNC_FLAGS));
 	priv->custom_divisor = new_serial.custom_divisor;
 
-	tty->low_latency = (priv->flags & ASYNC_LOW_LATENCY) ? 1 : 0;
 	write_latency_timer(port);
 
 check_and_exit:
@@ -1704,9 +1703,6 @@ static int ftdi_open(struct tty_struct *tty, struct usb_serial_port *port)
 	priv->rx_bytes = 0;
 	spin_unlock_irqrestore(&priv->rx_lock, flags);
 
-	if (tty)
-		tty->low_latency = (priv->flags & ASYNC_LOW_LATENCY) ? 1 : 0;
-
 	write_latency_timer(port);
 
 	/* No error checking for this (will get errors later anyway) */