The question is based on a false premise, that omnipotence means the ability to do anything. Rather omnipotence means posessing infinite power:
- almighty or infinite in power, as God.
- having very great or unlimited authority or power.
Having infinite power does not give one the ability to do anything. It only gives them the ability to do anything which is possible by force. No amount of power allows one to do the logically impossible: Draw a spherical square, or create an object so large it cannot be moved, sing the color purple, or any other logical impossibility.
See my answer on Philosophy.SE to a simliar question (which was originally here, but migrated).