It’s almost time to get fired up for “The House of the Dragon.” The “Game of Thrones” prequel series, based on George R.R. Martin’s “Fire & Blood,” will premiere Aug. 21 on HBO, the network announced Wednesday. “House of the Dragon” is set 200 years before the events of “Game of Thrones” and focuses on House Targaryen, ancestors of Emilia Clarke’s Daenerys Targaryen character. The series stars Paddy Considine, Olivia Cooke, Matt Smith, Emma D’Arcy, Fabien Frankel, Rhys Ifans, Steve Toussaint, Eve Best and Sonoya Mizuno. Martin announced in February that production on the first season had wrapp…