USB: cdc-acm, use tty_standard_install

This is a piece I missed the last time.

Do not copy the functionality all over the tree. Instead, use the
helper the tty layer provides us with.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Oliver Neukum <oneukum@suse.de>
Acked-by: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/class/cdc-acm.c

@@ -508,17 +508,12 @@ static int acm_tty_install(struct tty_driver *driver, struct tty_struct *tty)
 	if (!acm)
 		return -ENODEV;
 
-	retval = tty_init_termios(tty);
+	retval = tty_standard_install(driver, tty);
 	if (retval)
 		goto error_init_termios;
 
 	tty->driver_data = acm;
 
-	/* Final install (we use the default method) */
-	tty_driver_kref_get(driver);
-	tty->count++;
-	driver->ttys[tty->index] = tty;
-
 	return 0;
 
 error_init_termios: