Throughout various continuities, the Autobots are described as being a faction or governing body on Cybertron that existed long before the Decepticons rose up and declared war against them. Thus the Autobrand is something that long predates the Cybertronian war, so it would appear that the origins of who and how the logo was designed may have been lost to antiquity. It may be a lot like asking "Who created the alphabet?"; such things aren't attributed to any single individual, but rather to various civilisations throughout time. The Autobrand probably started off as a religious symbol (re: Primus' face), but evolved through time to become the Autobot insignia. If we compare it with ancient religious symbols on Earth, we don't know who exactly created these symbols, but all we know is that they have become symbols. Whose idea was it to use a crucifix as a symbol of Christianity, the Star of David for Judaism, the Swastika as a symbol for Hinduism/Buddhism/Jainism (then later modified as the logo of the Nazi party)?

I don't think it's really possible to determine which single individual created the Autobrand. Even if Ironhide walked around claiming that he made it, he'd been seen as a lunatic.

"Fact is, I invented kissing. It was during World War I and they were looking for a new way to spread germs..."
- Abraham Simpson (The Simpsons)