This patch implements a HID driver for the Corsair Vengeance K90 keyboard.

It fixes the behaviour of the keys using incorrect HID usage codes and exposes
the macro playback mode and current profile to the user space through sysfs
attributes. It also adds two LED class devices controlling the "record" LED and
the backlight.
Signed-off-by: Clément Vuchener <clement.vuchener@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>