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>

drivers/usb/serial/kobil_sct.c

@@ -324,7 +324,6 @@ static void kobil_read_int_callback(struct urb *urb)
 {
 	int result;
 	struct usb_serial_port *port = urb->context;
-	struct tty_struct *tty;
 	unsigned char *data = urb->transfer_buffer;
 	int status = urb->status;
 
@@ -333,8 +332,7 @@ static void kobil_read_int_callback(struct urb *urb)
 		return;
 	}
 
-	tty = tty_port_tty_get(&port->port);
-	if (tty && urb->actual_length) {
+	if (urb->actual_length) {
 
 		/* BEGIN DEBUG */
 		/*
@@ -354,9 +352,8 @@ static void kobil_read_int_callback(struct urb *urb)
 		/* END DEBUG */
 
 		tty_insert_flip_string(&port->port, data, urb->actual_length);
-		tty_flip_buffer_push(tty);
+		tty_flip_buffer_push(&port->port);
 	}
-	tty_kref_put(tty);
 
 	result = usb_submit_urb(port->interrupt_in_urb, GFP_ATOMIC);
 	dev_dbg(&port->dev, "%s - Send read URB returns: %i\n", __func__, result);