Freddy Krueger is stronger in dreams, in real-life he's weak. I think Loki can win both rounds, Freddy frequently struggled when taking on a group of teenagers in their dreams; Loki is obviously a stronger force than a group of teenagers.
Dreamworld Freddy would win IMO. Doubt that Loki has spells, that could help him. Even if he does, how would he conjure them? However, would being killed in his dreams work on Loki? Of course we see regular humans being killed in real life when killed by Freddy in their dreams. However, Loki is a Asgardian which means they are by many means stronger, and more durable than a normal human.
As for in real life, in Asgard Loki wins in a stomp. Freddy has no power there, and would get his teeth kicked in by the Norse god of mischief. The only scene where he had in power in real life that I can remember, is when he was in possession of the Necronomicon.
Freddy loses both rounds. The strongest people he has beaten have been a bunch of kids. He's NEVER faced someone with power or magical ability like Loki. To say nothing of the sizable, sizable gap in intelligence and cunning between the two. He'd be a minor demon at best in the MU. Loki puts Freddy's soul in a small jar and puts it on a shelf somewhere.