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/ir-usb.c b/drivers/usb/serial/ir-usb.c
index 171dae1..716930a 100644
--- a/drivers/usb/serial/ir-usb.c
+++ b/drivers/usb/serial/ir-usb.c
@@ -287,7 +287,6 @@
 {
 	struct usb_serial_port *port = urb->context;
 	unsigned char *data = urb->transfer_buffer;
-	struct tty_struct *tty;
 
 	if (!urb->actual_length)
 		return;
@@ -302,12 +301,8 @@
 	if (urb->actual_length == 1)
 		return;
 
-	tty = tty_port_tty_get(&port->port);
-	if (!tty)
-		return;
 	tty_insert_flip_string(&port->port, data + 1, urb->actual_length - 1);
-	tty_flip_buffer_push(tty);
-	tty_kref_put(tty);
+	tty_flip_buffer_push(&port->port);
 }
 
 static void ir_set_termios_callback(struct urb *urb)