CNN  —  The Kansas City Chiefs secured the No. 1 seed in the AFC with their franchise-record 15th victory after overwhelming the Pittsburgh Steelers on Christmas Day . With the top seed, the reigning back-to-back Super Bowl champion captured the lone first-round bye in the playoffs and home-field advantage. “I thought it was a full team performance, defense stepped up, offense stepped up. Everybody had their imprint on the game,” Chiefs quarterback Patrick Mahomes said after the game. “I told