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/usb/serial/quatech2.c b/drivers/usb/serial/quatech2.c
index d152be9..1e67fd8 100644
--- a/drivers/usb/serial/quatech2.c
+++ b/drivers/usb/serial/quatech2.c
@@ -697,7 +697,7 @@
 				escapeflag = true;
 				break;
 			case QT2_CONTROL_ESCAPE:
-				tty_buffer_request_room(tty, 2);
+				tty_buffer_request_room(&port->port, 2);
 				tty_insert_flip_string(tty, ch, 2);
 				i += 2;
 				escapeflag = true;
@@ -713,7 +713,7 @@
 		}
 
 		if (tty) {
-			tty_buffer_request_room(tty, 1);
+			tty_buffer_request_room(&port->port, 1);
 			tty_insert_flip_string(tty, ch, 1);
 		}
 	}