HP Inc. shares rallied Thursday after Warren Buffett’s Berkshire Hathaway Inc. revealed a new 121-million-share stake in HP worth about $4.2 billion. In a new filing, Berkshire said it now holds roughly an 11 percent ownership stake in HP, a major vote of confidence from one of the most famous and successful investors of all time. Bull & Bear Case On Thursday, Bank of America analyst Wamsi Mohan said Buffett is likely focused on HP’s attractive valuation, free cash flow profile and strong capital return program. Yet Mohan said there are plenty of points to the HP bear case as well. Mohan said HP benefited from the pandemic, and its earning growth and margins will likely decline in coming years. In addition, the rate and pace of its capital return will likely also slow after the company’s recent $3.3-billion buyout of Poly, he said. Finally, the PC market will likely experience …