The Elon Musk-backed artificial intelligence startup xAI is raising more financing than initially planned — including an equity investment from Nvidia Corp. — to bring its ongoing funding round to $20 billion, according to people with knowledge of the matter.The financing, which includes equity and debt, will be tied to the Nvidia graphics processing units that xAI plans to use in Colossus 2, said the people, who asked not to be identified because the information is private. That’s the name of i...