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/tty/serial/imx.c b/drivers/tty/serial/imx.c
index f60c402..be26345 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -518,7 +518,6 @@
 	unsigned int rx, flg, ignored = 0;
 	struct tty_struct *tty = sport->port.state->port.tty;
 	struct tty_port *port = &sport->port.state->port;
-	struct tty_struct *tty = port->tty;
 	unsigned long flags, temp;
 
 	spin_lock_irqsave(&sport->port.lock, flags);
@@ -576,7 +575,7 @@
 
 out:
 	spin_unlock_irqrestore(&sport->port.lock, flags);
-	tty_flip_buffer_push(tty);
+	tty_flip_buffer_push(port);
 	return IRQ_HANDLED;
 }