Instead of creating attributes one by one, define attribute_group array
and attach it to bus->dev_groups, so that all needed attributes are created
automatically when a new device is registered on the bus.

Also switch to using standard DEVICE_ATTR_RO() macros.
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>