led-panel: Make the output power jumper selection safer

[esden]

Currently the 3v3/5v jumpers are both normally closed. This should be changed and we have two options:

• Use a 3 way jumper where the 3v3 side is normally closed and 5v normally open. The user will have to pay attention to jumpers and reconfigure them if they want to use 5v output. (most development boards don't have the 5v aux connector the way icebreaker has it)
• Keep the jumpers closed but add a diode or some other more fancy circuit to direct power. The disadvantage is that it adds more parts and will make the PMOD more expensive.

If you have some other ideas let me know. :)

[esden]

I have changed that. Now there is 3v3 normally closed and 5v normally open jumper. This requires the user to actively change the jumper increasing the probability that they will do it right. Also from the testing so far we were able to drive most panels using 3v3 signals. 5v and level shifting has so far been more of an assurance than a requirement. :)