HID: roccat: use class for char device for sysfs attribute creation

Adding sysfs attributes to an already created device raises no userland
notification. Now the device drivers associate the devices attributes
with a class and use this for roccat event char device creation.

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