Not entirely made up. In Tolkien's world. Azog was indeed the leader of the orcs in Moria and he did behead Thror. However, Tolkien's story has Azog killed by Dain in that same battle. The scene at the end of the first Hobbit movie did take place in the book, but Azog was not present--if I remember right, they were just treed by some random goblins, who sang a cheery song :)