* CDP consortium to bid for Atlantia’s unit by Feb. 24 * Atlantia’s unit valued 9 bln euros in CDP offer, sources say * CDP says consortium could buy up to 100% of Autostrade MILAN, Feb 23 (Reuters) - Cassa Depositi e Prestiti (CDP) on Tuesday gave the go-ahead to submit an offer to buy Atlantia’s 88% stake in Autostrade per l’Italia unit, CDP said, after two sources told Reuters the bid would value 100% of Autostrade at 9 billion euros. Italian state lender CDP, which will file its binding bid with its investment fund partners Macquarie and Blackstone, did not disclose the financial details of the bid due to be presented by Wednesday.