OKLAHOMA CITY — Severe storms and tornadoes battered Oklahoma early Sunday, tossing cars and ripping roofs off buildings in the middle of the night and leaving tens of thousands of homes and businesses without power. Among numerous injuries, 11 people required hospitalization, authorities said. Much of the damage occurred in and around the state capital, Oklahoma City, near the state’s center, although there were reports of damage at various points around the state and early morning storms set off tornado warnings that extended south to the Arkansas state line.