Even if we assume that Psalm 22 is a prophecy of the messiahs death, this is no reason to recite the first verse. Instead of shedding light on his messiahship, this actually casts more doubt. If he truly was the messiah, the son of god, then certainly he would have known this is what his mission had to come to. But not only here, but in the garden of Gethsemane, he showed intense doubt, fear, and anxiety at what he was about to face. Surely he would have gone into it with more courage than that. But him crying out, asking why god had forsaken him, for all to hear, would certainly have the effect on his listeners that he was unsure of his mission and station. If this event actually happened, then anyone could have gone back to this Psalm, and noticed all the similarities, and it would have indicated the importance of it, all without Jesus having quoted the first verse on the cross. This does him more of a disservice, in light of Christian dogma, than it having anything to do with pointing at a supposed prophecy.