It is a USB port, not sure how much power an iPad needs and some USB ports don't supply enough power so you will have to try it...however, there is a normal power socket as well near the floor you could use if the USB port doesn't supply enough power.

From a post by Sammyh25 (#8) on this thread

"I'm currently doing the training for Pursers and CSDs on the new Thales IFE system, so....

The two USB ports in First, Club and WT+ are there for charging USB devices (perfectly ok to leave them plugged in if you are sleeping) and for loading photographs onto the system (JPEG files only). U cannot listen to music or watch a movie via the USB ports...

The RCA ports (phono in the UK), red/white & yellow are in all cabins apart from W/T, and these allow you to connect a video camera, or even your iPod/iPhone (cables available from all good retailers) to the Thales system and then watch your movie on screen via our IFE. In W/T only the yellow plug is available so you can watch your movie on the IFE screen but you must plug your headset into your device to hear the soundtrack."

So although I don't remember two USB ports on the 777's I flew in NF maybe I just overlooked them...hope this helps.