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/8250/8250.c b/drivers/tty/serial/8250/8250.c
index 5fb6577..0d771ec 100644
--- a/drivers/tty/serial/8250/8250.c
+++ b/drivers/tty/serial/8250/8250.c
@@ -1323,7 +1323,6 @@
 serial8250_rx_chars(struct uart_8250_port *up, unsigned char lsr)
 {
 	struct uart_port *port = &up->port;
-	struct tty_struct *tty = port->state->port.tty;
 	unsigned char ch;
 	int max_count = 256;
 	char flag;
@@ -1388,7 +1387,7 @@
 		lsr = serial_in(up, UART_LSR);
 	} while ((lsr & (UART_LSR_DR | UART_LSR_BI)) && (max_count-- > 0));
 	spin_unlock(&port->lock);
-	tty_flip_buffer_push(tty);
+	tty_flip_buffer_push(&port->state->port);
 	spin_lock(&port->lock);
 	return lsr;
 }