instead of messing with ide_module_t, we put ide_driver_t themselves on
a (cyclic) list - said list being the only use of ide_module_t for
high-level drivers.  ide_register_module()/ide_unregister_module() takes
ide_driver_t now (renamed to ide_register_driver()).  /proc/ide/drivers
switched to use of that cyclic list and uses seq_file instead of old
home-grown code.