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/cypress_m8.c b/drivers/usb/serial/cypress_m8.c
index ac14e3e..8efa19d 100644
--- a/drivers/usb/serial/cypress_m8.c
+++ b/drivers/usb/serial/cypress_m8.c
@@ -1214,10 +1214,10 @@
 		spin_unlock_irqrestore(&priv->lock, flags);
 
 	/* process read if there is data other than line status */
-	if (tty && bytes > i) {
+	if (bytes > i) {
 		tty_insert_flip_string_fixed_flag(&port->port, data + i,
 				tty_flag, bytes - i);
-		tty_flip_buffer_push(tty);
+		tty_flip_buffer_push(&port->port);
 	}
 
 	spin_lock_irqsave(&priv->lock, flags);