POP star Herman, of the Hermits, met his new sister yesterday and was landed with a problem.     He was given the job of choosing a name for the two-day-old baby.     Eighteen-year-old Herman, whose real name is Peter Noone, said: "I haven't got a clue what to call her. I had thought of plenty of boys' names, but not one for a girl."     His mother, Mrs. Joan Noone, 37, of Chestnut Avenue, Huyton, Liverpool - this is her fourth child - said: "We all decided that Peter should name the baby."     But Peter finds it easier making hit records.