I'm 6'4" and had the same problem. As others have stated, you *can* move the headrest up and down with the power button on the side of the seat. However, what I had more of an issue with was the headrest moving in and out. Because the headrests are active (for collision mitigation purposes) they no longer tilt like they did on older cars, but they do *manually* go in and out (closer/further from the front of the car). There is a button on the inboard side of the headrest. Press and hold it and while doing so you can move the headrest in and out.
I've noticed that the headrest seems to move forward (it powers down as well) when you tip the seats forward to access the back seat so I find myself adjusting it quite a bit after moving the seats.