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/aircable.c b/drivers/usb/serial/aircable.c
index 3bb1f8f..6e320ce 100644
--- a/drivers/usb/serial/aircable.c
+++ b/drivers/usb/serial/aircable.c
@@ -140,16 +140,11 @@
 {
 	struct usb_serial_port *port = urb->context;
 	char *data = (char *)urb->transfer_buffer;
-	struct tty_struct *tty;
 	int has_headers;
 	int count;
 	int len;
 	int i;
 
-	tty = tty_port_tty_get(&port->port);
-	if (!tty)
-		return;
-
 	has_headers = (urb->actual_length > 2 && data[0] == RX_HEADER_0);
 
 	count = 0;
@@ -160,8 +155,7 @@
 	}
 
 	if (count)
-		tty_flip_buffer_push(tty);
-	tty_kref_put(tty);
+		tty_flip_buffer_push(&port->port);
 }
 
 static struct usb_serial_driver aircable_device = {