HID: roccat: propagate special events of roccat hardware to userspace

Module roccat is a char device used to report special events of roccat hardware
to userland. These events include requests for on-screen-display of profile or
dpi settings or requests for execution of macro sequences that are not stored
in device. The information in these events depends on hid device implementation
and contains data that is not available in a single hid event or else hidraw
could have been used.

It is inspired by hidraw, but uses only one circular buffer for all readers.
The device is as generic as possible so that the functionality is usable by all
(kone and upcomming) roccat device drivers.

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