Not officially confirmed, but he saw Matt fighting without a mask in the final battle. Even from as far away as he was, he was using a sniper scope so it'd be really surprising if he hadn't seen Matt's face. So if he hadn't figured it out by then, I imagine he'd know after that. However, we didn't hear him say anything like "Matt Murdock is Daredevil", so I'll happily be reading fics where he does or doesn't know and enjoying both scenarios. ;)