China’s chip stocks have staged a world-beating rally in the past few months on the nation’s self-sufficiency push, but some investors are beginning to balk at their lofty valuations.Cambricon Technologies Corp., dubbed “China’s Nvidia” by retail investors, is trading at an earnings multiple nearly five times that of the more famous AI chip designer. Semiconductor Manufacturing International Corp. and Hua Hong Semiconductor Ltd. are priced at premiums to major global foundries....