MADONNA has been given the green light to adopt a second orphan from Malawi — a 13-month-old girl called Mercy. She’s been told she can take the “smiling angel” as a sister to David Banda, her first child from the African nation.It follows months of legal wrangling over the adoption of 22-month-old David.And to ensure all goes smoothly this time, Madge, 49, has told her lawyer in Malawi, Alan Chinula, to “cover all legal bases” before she collects Mercy next April.Madge insisted she wanted to adopt a sister for David “to redress the balance”. Officials asked her