Sales are reportedly weak at a key partner.Shares of Arm Holdings (ARM -4.85%) were heading lower on reports of disappointing early sales results from Apple's (AAPL -2.91%) iPhone 16, the new smartphone it just released that will include Apple Intelligence, its new artificial intelligence (AI) platform.Arm makes roughly half of its royalty revenue from the iPhone, so it wasn't surprising to see the stock reacting poorly to the news.Arm stock closed down 4.9%, while Apple lost 2.9%. iPhone 16 is off to a wea ...