MINNEAPOLIS—Before Brandon Powell joined the Los Angeles Rams last month, his fifth team in four NFL seasons, he read books on the beach near his Florida home while waiting for yet another chance. This was quite the chapter, helping clinch a spot for the Rams in the playoffs. Powell returned a punt 61 yards for a touchdown in the third quarter to lift the Rams at just the right time on the way to a 30-23 victory over the Vikings on Sunday that also secured a postseason berth for Arizona. “I just did the easy part. I just caught the ball and ran the ball up the sideline,” said Powell, who was on the active roster for the Rams for only the fourth time. Little has been easy lately for the Rams (11-4), who won their fourth straight game and passed the Cardinals (10-5) for first place in the NFC …