TTY: switch tty_flip_buffer_push

Now, we start converting tty buffer functions to actually use
tty_port. This will allow us to get rid of the need of tty in many
call sites. Only tty_port will needed and hence no more
tty_port_tty_get in those paths.

Now, the one where most of tty_port_tty_get gets removed:
tty_flip_buffer_push.

IOW we also closed all the races in drivers not using tty_port_tty_get
at all yet.

Also we move tty_flip_buffer_push declaration from include/linux/tty.h
to include/linux/tty_flip.h to all others while we are changing it
anyway.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/usb/serial/metro-usb.c b/drivers/usb/serial/metro-usb.c
index 6264f39..bf3c7a2 100644
--- a/drivers/usb/serial/metro-usb.c
+++ b/drivers/usb/serial/metro-usb.c
@@ -95,7 +95,6 @@
 {
 	struct usb_serial_port *port = urb->context;
 	struct metrousb_private *metro_priv = usb_get_serial_port_data(port);
-	struct tty_struct *tty;
 	unsigned char *data = urb->transfer_buffer;
 	int throttled = 0;
 	int result = 0;
@@ -124,15 +123,13 @@
 
 
 	/* Set the data read from the usb port into the serial port buffer. */
-	tty = tty_port_tty_get(&port->port);
-	if (tty && urb->actual_length) {
+	if (urb->actual_length) {
 		/* Loop through the data copying each byte to the tty layer. */
 		tty_insert_flip_string(&port->port, data, urb->actual_length);
 
 		/* Force the data to the tty layer. */
-		tty_flip_buffer_push(tty);
+		tty_flip_buffer_push(&port->port);
 	}
-	tty_kref_put(tty);
 
 	/* Set any port variables. */
 	spin_lock_irqsave(&metro_priv->lock, flags);