TTY: convert more flipping functions

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.

Now 4 string flipping ones are on turn:
* tty_insert_flip_string_flags
* tty_insert_flip_string_fixed_flag
* tty_prepare_flip_string
* tty_prepare_flip_string_flags

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index 0a373b3..0416d95 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -2032,7 +2032,7 @@
 				tty_insert_flip_char(tty, *ch, flag);
 		}
 	} else {
-		tty_insert_flip_string_fixed_flag(tty, ch, flag, len);
+		tty_insert_flip_string_fixed_flag(&port->port, ch, flag, len);
 	}
 
 	return len;