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/digi_acceleport.c b/drivers/usb/serial/digi_acceleport.c
index 45d4af6..efbc403 100644
--- a/drivers/usb/serial/digi_acceleport.c
+++ b/drivers/usb/serial/digi_acceleport.c
@@ -1455,8 +1455,8 @@
 		/* data length is len-1 (one byte of len is port_status) */
 		--len;
 		if (len > 0) {
-			tty_insert_flip_string_fixed_flag(tty, data, flag,
-									len);
+			tty_insert_flip_string_fixed_flag(&port->port, data,
+					flag, len);
 			tty_flip_buffer_push(tty);
 		}
 	}