By Mollie Quirk Prince Harry and Meghan Markle’s Nigeria trip is poised to “boost their popularity, value and brand”, according to a royal expert. The Duke and Duchess of Sussex touched down in Nigeria in the early hours of Friday morning, following Prince Harry’s short but sweet trip to the United Kingdom. The couple are visiting the West African country on a 72-hour whistle-stop tour. After Harry’s solo trip to the UK, he reunited with his wife at Heathrow. Meghan landed in the UK on Thursday after she flew in from Los Angeles. She was seen waiting for Harry at the airport in the VIP Windsor…