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>

drivers/net/caif/caif_serial.c

@@ -91,7 +91,7 @@ static inline void update_tty_status(struct ser_device *ser)
 		ser->tty->hw_stopped << 4 |
 		ser->tty->flow_stopped << 3 |
 		ser->tty->packet << 2 |
-		ser->tty->low_latency << 1 |
+		ser->tty->port->low_latency << 1 |
 		ser->tty->warned;
 }
 static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty)