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/belkin_sa.c b/drivers/usb/serial/belkin_sa.c
index 7ba2c0b..84217e7 100644
--- a/drivers/usb/serial/belkin_sa.c
+++ b/drivers/usb/serial/belkin_sa.c
@@ -242,7 +242,6 @@
 {
 	struct usb_serial_port *port = urb->context;
 	struct belkin_sa_private *priv = usb_get_serial_port_data(port);
-	struct tty_struct *tty;
 	unsigned char *data = urb->transfer_buffer;
 	unsigned long flags;
 	unsigned char status;
@@ -259,10 +258,6 @@
 	if (!urb->actual_length)
 		return;
 
-	tty = tty_port_tty_get(&port->port);
-	if (!tty)
-		return;
-
 	if (status & BELKIN_SA_LSR_ERR) {
 		/* Break takes precedence over parity, which takes precedence
 		 * over framing errors. */
@@ -281,8 +276,7 @@
 
 	tty_insert_flip_string_fixed_flag(&port->port, data, tty_flag,
 							urb->actual_length);
-	tty_flip_buffer_push(tty);
-	tty_kref_put(tty);
+	tty_flip_buffer_push(&port->port);
 }
 
 static void belkin_sa_set_termios(struct tty_struct *tty,