Like Jimmy Carter once did, Iran's Ayatollah Ruhollah Khomeini has admitted he has a little lust in his heart. Khomeini, 88, in an address Monday to the world's 1 billion Moslems on the eve of Iran's new year, said people should concentrate on God's will, not earthly pleasures. "In his lifetime, man is afflicted with carnal desires," Khomeini said. "He needs self-discipline and I, as the speaker of these words, have not succeeded in this task."