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/tty/serial/kgdb_nmi.c b/drivers/tty/serial/kgdb_nmi.c
index ba2ef62..26a50b0 100644
--- a/drivers/tty/serial/kgdb_nmi.c
+++ b/drivers/tty/serial/kgdb_nmi.c
@@ -202,7 +202,6 @@
 static void kgdb_nmi_tty_receiver(unsigned long data)
 {
 	struct kgdb_nmi_tty_priv *priv = (void *)data;
-	struct tty_struct *tty;
 	char ch;
 
 	tasklet_schedule(&priv->tlet);
@@ -210,16 +209,9 @@
 	if (likely(!kgdb_nmi_tty_enabled || !kfifo_len(&priv->fifo)))
 		return;
 
-	/* Port is there, but tty might be hung up, check. */
-	tty = tty_port_tty_get(kgdb_nmi_port);
-	if (!tty)
-		return;
-
 	while (kfifo_out(&priv->fifo, &ch, 1))
 		tty_insert_flip_char(&priv->port, ch, TTY_NORMAL);
-	tty_flip_buffer_push(priv->port.tty);
-
-	tty_kref_put(tty);
+	tty_flip_buffer_push(&priv->port);
 }
 
 static int kgdb_nmi_tty_activate(struct tty_port *port, struct tty_struct *tty)