LOS ANGELES — Adam Rich, the child actor with a pageboy mop-top who charmed TV audiences in the late 1970s as “America’s little brother” on “Eight is Enough,” has died. Rich died Saturday in the Brentwood section of Los Angeles, said Lt. Aimee Earl of the Los Angeles County Medical-Examiner Coroner’s office. Rich had a limited acting career after playing Nicholas Bradford, the youngest of eight children, on the ABC hit dramedy that ran from from 1977 to 1981.