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/arch/um/drivers/line.c b/arch/um/drivers/line.c
index 9ffc28b..f1b3857 100644
--- a/arch/um/drivers/line.c
+++ b/arch/um/drivers/line.c
@@ -19,11 +19,10 @@
 {
 	struct chan *chan = data;
 	struct line *line = chan->line;
-	struct tty_struct *tty = tty_port_tty_get(&line->port);
 
 	if (line)
-		chan_interrupt(line, tty, irq);
-	tty_kref_put(tty);
+		chan_interrupt(line, irq);
+
 	return IRQ_HANDLED;
 }
 
@@ -234,7 +233,7 @@
 	struct line *line = tty->driver_data;
 
 	line->throttled = 0;
-	chan_interrupt(line, tty, line->driver->read_irq);
+	chan_interrupt(line, line->driver->read_irq);
 
 	/*
 	 * Maybe there is enough stuff pending that calling the interrupt