TTY: move low_latency to tty_port

One point is to have less places where we actually need tty pointer.
The other is that low_latency is bound to buffer processing and
buffers are now in tty_port. So it makes sense to move low_latency to
tty_port too.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c
index 31873e4..1bfe97a 100644
--- a/drivers/tty/tty_buffer.c
+++ b/drivers/tty/tty_buffer.c
@@ -364,7 +364,7 @@
 {
 	struct tty_bufhead *buf = &tty->port->buf;
 	unsigned long flags;
-	WARN_ON(tty->low_latency);
+	WARN_ON(tty->port->low_latency);
 
 	spin_lock_irqsave(&buf->lock, flags);
 	if (buf->tail != NULL)
@@ -538,7 +538,7 @@
  */
 void tty_flush_to_ldisc(struct tty_struct *tty)
 {
-	if (!tty->low_latency)
+	if (!tty->port->low_latency)
 		flush_work(&tty->port->buf.work);
 }
 
@@ -547,7 +547,8 @@
  *	@tty: tty to push
  *
  *	Queue a push of the terminal flip buffers to the line discipline. This
- *	function must not be called from IRQ context if tty->low_latency is set.
+ *	function must not be called from IRQ context if port->low_latency is
+ *	set.
  *
  *	In the event of the queue being busy for flipping the work will be
  *	held off and retried later.
@@ -565,7 +566,7 @@
 		buf->tail->commit = buf->tail->used;
 	spin_unlock_irqrestore(&buf->lock, flags);
 
-	if (tty->low_latency)
+	if (tty->port->low_latency)
 		flush_to_ldisc(&buf->work);
 	else
 		schedule_work(&buf->work);