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/serial/ioc3_serial.c b/drivers/tty/serial/ioc3_serial.c
index 0f25ce4..edbdc4e 100644
--- a/drivers/tty/serial/ioc3_serial.c
+++ b/drivers/tty/serial/ioc3_serial.c
@@ -1000,7 +1000,7 @@
 
 	the_port->ignore_status_mask = N_ALL_INPUT;
 
-	state->port.tty->low_latency = 1;
+	state->port.low_latency = 1;
 
 	if (iflag & IGNPAR)
 		the_port->ignore_status_mask &= ~(N_PARITY_ERROR