HID: roccat: change kone_driver_version to kone_abi_version

Renamed the sysfs attribute kone_driver_version to kone_abi_version and
simplified returned data to integer.

Signed-off-by: Stefan Achatz <erazor_de@users.sourceforge.net>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>