TTY: move tty buffers to tty_port

So this is it. The big step why we did all the work over the past
kernel releases. Now everything is prepared, so nothing protects us
from doing that big step.

           |  |            \  \ nnnn/^l      |  |
           |  |             \  /     /       |  |
           |  '-,.__   =>    \/   ,-`    =>  |  '-,.__
           | O __.´´)        (  .`           | O __.´´)
            ~~~   ~~          ``              ~~~   ~~
The buffers are now in the tty_port structure and we can start
teaching the buffer helpers (insert char/string, flip etc.) to use
tty_port instead of tty_struct all around.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/tty_port.c

@@ -21,6 +21,7 @@
 void tty_port_init(struct tty_port *port)
 {
 	memset(port, 0, sizeof(*port));
+	tty_buffer_init(port);
 	init_waitqueue_head(&port->open_wait);
 	init_waitqueue_head(&port->close_wait);
 	init_waitqueue_head(&port->delta_msr_wait);
@@ -126,6 +127,7 @@ static void tty_port_destructor(struct kref *kref)
 	struct tty_port *port = container_of(kref, struct tty_port, kref);
 	if (port->xmit_buf)
 		free_page((unsigned long)port->xmit_buf);
+	tty_buffer_free_all(port);
 	if (port->ops->destruct)
 		port->ops->destruct(port);
 	else