tty: Mark generic_serial users as BROKEN

There isn't much else I can do with these. I can find no hardware for any
of them and no users. The code is broken.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>