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/arc_uart.c b/drivers/tty/serial/arc_uart.c
index b468601..da73422 100644
--- a/drivers/tty/serial/arc_uart.c
+++ b/drivers/tty/serial/arc_uart.c
@@ -211,12 +211,8 @@
 
 static void arc_serial_rx_chars(struct arc_uart_port *uart)
 {
-	struct tty_struct *tty = tty_port_tty_get(&uart->port.state->port);
 	unsigned int status, ch, flg = 0;
 
-	if (!tty)
-		return;
-
 	/*
 	 * UART has 4 deep RX-FIFO. Driver's recongnition of this fact
 	 * is very subtle. Here's how ...
@@ -252,10 +248,8 @@
 		uart_insert_char(&uart->port, status, RXOERR, ch, flg);
 
 done:
-		tty_flip_buffer_push(tty);
+		tty_flip_buffer_push(&uart->port.state->port);
 	}
-
-	tty_kref_put(tty);
 }
 
 /*