For all the attention on Apple Inc.’s iPhone sales, a less glamorous item could be the big driver of the stock after earnings.JPMorgan’s Samik Chatterjee wrote that Apple’s AAPL, +0.87% margins could be the big swing factor for Apple’s stock in the wake of its Thursday afternoon report. Don’t miss: This fund is shorting Apple — and just bet against another popular AI stock“Premiumization of the iPhone with price-mix tailwinds along with tight cost management are helping hardware margins, and the mix change ...