Jensen Huang says Nvidia bans political discourse at work. In the same All-In interview, the President of the United States called his cell phone, and Jensen put him on speakerphone for the whole room. Both clips are the same policy. No company on earth has more riding on politics than Nvidia. Washington's export rules took its China data center business from $19.67 billion a year to effectively zero. One licensing decision forced a $4.5 billion writedown in a single quarter. Then Beijing…