Surrey Bancorp said its earnings for the fourth quarter more than doubled in 2012 to $976,399 from $422,530 a year earlier. For all of 2012, net income was $2.8 million, a 23 percent increase from 2011. An increase in net interest income of 5.3 percent and a substantial drop in the amount set aside to cover potential loan losses contributed to the increased earnings, the bank said. The Mount Airy-based Surrey Bancorp (OTC: SRYB) is one of the most active U.S. Small Business Administration lenders…