From a wikipedia article:[1]
During his career, Mercury's flamboyant stage performances sometimes led journalists to allude to his sexuality. Dave Dickson, reviewing Queen's performance at Wembley Arena in 1984 for Kerrang!, noted Mercury's "camp" addresses to the audience and even described him as a "posing, pouting, posturing tart."
I think it may not refer to "camp" as a place (or encampment), but to a gay-related slang that means "a man who behaves in an ostentatiously effeminate way" according to the Google Translator.