The scores of immigrants who passed through Ellis Island at the turn of the century remember it as America's "golden door. " But to Naoye Suzuki, it was a locked door. During World War II, Suzuki, a dual citizen of the U. S. and Japan, was imprisoned there for a year and a half as an "enemy alien. " For Suzuki, 79, who revisited Ellis Island two weeks ago for a special exhibit chronicling those dark days, memories of that time arouse feelings of sadness and even happiness but not bitterness.