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/ar933x_uart.c

@@ -298,10 +298,8 @@ static void ar933x_uart_set_termios(struct uart_port *port,
 static void ar933x_uart_rx_chars(struct ar933x_uart_port *up)
 {
 	struct tty_port *port = &up->port.state->port;
-	struct tty_struct *tty;
 	int max_count = 256;
 
-	tty = tty_port_tty_get(port);
 	do {
 		unsigned int rdata;
 		unsigned char ch;
@@ -324,10 +322,7 @@ static void ar933x_uart_rx_chars(struct ar933x_uart_port *up)
 			tty_insert_flip_char(port, ch, TTY_NORMAL);
 	} while (max_count-- > 0);
 
-	if (tty) {
-		tty_flip_buffer_push(tty);
-		tty_kref_put(tty);
-	}
+	tty_flip_buffer_push(port);
 }
 
 static void ar933x_uart_tx_chars(struct ar933x_uart_port *up)