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/net/usb/hso.c b/drivers/net/usb/hso.c
index d235ca0..f902a14 100644
--- a/drivers/net/usb/hso.c
+++ b/drivers/net/usb/hso.c
@@ -2035,24 +2035,23 @@
 	tty = tty_port_tty_get(&serial->port);
 
 	/* Push data to tty */
-	if (tty) {
-		write_length_remaining = urb->actual_length -
-			serial->curr_rx_urb_offset;
-		D1("data to push to tty");
-		while (write_length_remaining) {
-			if (test_bit(TTY_THROTTLED, &tty->flags)) {
-				tty_kref_put(tty);
-				return -1;
-			}
-			curr_write_len = tty_insert_flip_string(&serial->port,
-				urb->transfer_buffer + serial->curr_rx_urb_offset,
-				write_length_remaining);
-			serial->curr_rx_urb_offset += curr_write_len;
-			write_length_remaining -= curr_write_len;
-			tty_flip_buffer_push(tty);
+	write_length_remaining = urb->actual_length -
+		serial->curr_rx_urb_offset;
+	D1("data to push to tty");
+	while (write_length_remaining) {
+		if (tty && test_bit(TTY_THROTTLED, &tty->flags)) {
+			tty_kref_put(tty);
+			return -1;
 		}
-		tty_kref_put(tty);
+		curr_write_len = tty_insert_flip_string(&serial->port,
+			urb->transfer_buffer + serial->curr_rx_urb_offset,
+			write_length_remaining);
+		serial->curr_rx_urb_offset += curr_write_len;
+		write_length_remaining -= curr_write_len;
+		tty_flip_buffer_push(&serial->port);
 	}
+	tty_kref_put(tty);
+
 	if (write_length_remaining == 0) {
 		serial->curr_rx_urb_offset = 0;
 		serial->rx_urb_filled[hso_urb_to_index(serial, urb)] = 0;