Manga isn't canon. And it's called the Fierce Deity's Mask. Deity means "god", dude. And the Light Spirits in TP had to come from somewhere.
Yes, deity does mean "god" but notice that the actual meaning is in lowercase, not uppercase. If you look it up in a dictionary it will say "god" in lowercase for its meaning. That means a lesser God. God of Light and God of Darkness seem like they would be full blown Gods, but a deity is just a god, not a God, if you get the difference.
Also, the Light Spirits were probably created by the Goddesses, just like everything else.
The fact that there is no God of Light spoken of is a good indication that there isn't one.
Plus, does it say anywhere in the games that there ISN'T a God of Light.
It also doesn't say anywhere in the game that the Mushroom Kingdom doesn't exist, but that's not evidence that it could be in the same universe as Hyrule.
God of Light has never been mentioned anywhere in the series...that's probably a good indication that there isn't one....yet, at least.
And with all of the chaos Majora's Mask caused, and the ghost Flat referring to him as the Devil, how could he not be the God of Darkness?
Major has caused chaos and destruction in one game. Ganon/dorf has made multiple appearances and is only ever referred to as a King of something (King of Evil, the Dark Realm etc..). Ganon/dorf has done many more terrible things than Majora has and is no at all considered a God of Darkness or anything of the sort.
Also, Ganondorf was never "chosen" by anyone to do anything. He stole the Triforce of Power in OoT because he was evil and greedy, and wanted to rule the world.
The Zelda games do deal with fate A LOT. Link is always the fated/destined person to save Hyrule. If his fate of being the hero is predetermined then it can easily be assumed that everyone is fated into their rolls. This means that Ganon/dorf was fated to steal the Triforce of Power (ToP). If he was fated to steal the ToP then he definitely was "chosen" for it, even if the way he was chosen doesn't seem like it.
Also, in TP, he doesn't steal the ToP. It just appears to him, randomly, when he is on the verge of death.