USB: option: fix memory leak

commit b9c3aab3 upstream.

Fix memory leak introduced by commit 383cedc3 ("USB: serial:
full autosuspend support for the option driver") which allocates
usb-serial data but never frees it.

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>