HID: logitech-dj: rename "gaming" receiver to "lightspeed"

This should help people identify the receiver. there are several receivers used
in gaming mice. the "lightspeed" technology is pretty well advertise so this
won't just be an obscure name.

Signed-off-by: Filipe Laíns <lains@archlinux.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>