Hayya Ala Khairil 'Amal is part of the Athan أذان of the Prophet (SAWA) and even in the time of the rule of Abi Bakr, but it was removed by Omar Ibn al-Khattab and replaced in morning Athan by Al-Salaat Khairun Min al-Nawm.
Al-Sunan al-Kubera by al-Bayhaqi Hadeeth 1847 narrated that the original Athan was with Hayya Ala Khairil Amal. All Ahlul Bayt (AS) used to mention it in Athan. Many of Sahabah used to say it even after Omar banned it.
Abdullah Ibn Omar used to say Hayya Ala Khairil Amal in the Athan after Hayya Alal Falah. ( Al-Mussannaf of Abdul Razzaq, Hadeeth 1732 and Al-Mussannaf by Ibn Abi Shayba , Hadeeth 2224).
Al-Layth Ibn Sa'd used to mention Hayya Al Khairil Amal in Athan ( Al-Sunan Al-Kubera by al-Bayhaqi Hadeeth 1845).