By Selena Li and Carolyn Cohn HONG KONG/LONDON (Reuters) -Prudential PLC notched up a 16% rise in 2021 operating profit after it strengthened its focus on Asia, though it warned of implications for global markets and the economy from Russia’s invasion of Ukraine. Uncertainties triggered by the crisis in Ukraine have prompted insurers to review their risk exposure. Prudential’s investment exposure through its Eastspring asset management unit is minimal, chief financial officer Mark FitzPatrick told a media call. However group chief executive Mike Wells warned, “The current conflict in Ukraine c…