By Timothy Gardner WASHINGTON (Reuters) -Robert McFarlane, a White House adviser who tapped Saudi royals to fund a covert war in Nicaragua and flew on a secret mission to sell arms to Iran in the scandal that shook Ronald Reagan’s presidency, has died. He was 84. McFarlane, who was in Michigan visiting family, died on Thursday of complications from a prior illness, his family said in a statement. McFarlane first worked in the White House under Richard Nixon, as a military aide to foreign policy chief Henry Kissinger, after serving two tours in Vietnam as a Marine officer. Quiet and poker-faced…