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/ioc4_serial.c b/drivers/tty/serial/ioc4_serial.c
index 86f64ed..e2520ab 100644
--- a/drivers/tty/serial/ioc4_serial.c
+++ b/drivers/tty/serial/ioc4_serial.c
@@ -2340,7 +2340,6 @@
  */
 static void receive_chars(struct uart_port *the_port)
 {
-	struct tty_struct *tty;
 	unsigned char ch[IOC4_MAX_CHARS];
 	int read_count, request_count = IOC4_MAX_CHARS;
 	struct uart_icount *icount;
@@ -2350,11 +2349,8 @@
 	/* Make sure all the pointers are "good" ones */
 	if (!state)
 		return;
-	if (!state->port.tty)
-		return;
 
 	spin_lock_irqsave(&the_port->lock, pflags);
-	tty = state->port.tty;
 
 	request_count = tty_buffer_request_room(&state->port, IOC4_MAX_CHARS);
 
@@ -2369,7 +2365,7 @@
 
 	spin_unlock_irqrestore(&the_port->lock, pflags);
 
-	tty_flip_buffer_push(tty);
+	tty_flip_buffer_push(&state->port);
 }
 
 /**