TTY: switch tty_buffer_request_room to tty_port

Now, we start converting tty buffer functions to actually use
tty_port. This will allow us to get rid of the need of tty pointer in
many call sites. Only tty_port will be needed and hence no more
tty_port_tty_get calls in those paths.

Here we start with tty_buffer_request_room.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c
index 45d9161..f897332 100644
--- a/drivers/tty/tty_buffer.c
+++ b/drivers/tty/tty_buffer.c
@@ -235,7 +235,7 @@
 
 /**
  *	tty_buffer_request_room		-	grow tty buffer if needed
- *	@tty: tty structure
+ *	@port: tty port structure
  *	@size: size desired
  *
  *	Make at least size bytes of linear space available for the tty
@@ -243,9 +243,8 @@
  *
  *	Locking: Takes port->buf.lock
  */
-int tty_buffer_request_room(struct tty_struct *tty, size_t size)
+int tty_buffer_request_room(struct tty_port *port, size_t size)
 {
-	struct tty_port *port = tty->port;
 	unsigned long flags;
 	int length;