Go ahead and use it. The chipset will only use 3.3GB, but having 2x2 gives you the performance boost from dual channel memory. Lots of people on this board use such configurations. I only use 2.5GB, but many have used and continue to use 2x2. The hardware supports more than what Apple says it does.
Also see yesterday's thread with the same question:
https://forums.macrumors.com/threads/626346/