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>

drivers/tty/serial/mcf.c

@@ -310,7 +310,7 @@ static void mcf_rx_chars(struct mcf_uart *pp)
 		uart_insert_char(port, status, MCFUART_USR_RXOVERRUN, ch, flag);
 	}
 
-	tty_flip_buffer_push(port->state->port.tty);
+	tty_flip_buffer_push(&port->state->port);
 }
 
 /****************************************************************************/