I2O: remove i2o_device_class_interface misuse

The intent of class interfaces was to provide different
'views' at the same object, not just run some code every
time a new class device is registered. Kill interface
structure, make class core register default attributes
and set up sysfs links right when registering class
devices.
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>