That doesn't follow from God's actions. We know what the text says, what Solomon requested and what God granted. We see God responding to Solomon's request in 1 Kings 3:11b. God said Solomon requested "discernment in administering justice." That's what God said of his request.
We also have a list of items from God that Solomon could have asked for but didn't, further demonstrating his selfless request. God said "I will give you what you have not asked for-both riches and honor-so that in your lifetime you will have no equal among kings."
God said Solomon didn't ask for riches, honor, long life, wealth or the death of his enemies. It's almost like God knew you and I were going to have this discussion. Here is God laying it all out for us. The more we look at this the more selfless his request appears.
We can't with certainty say it was a totaly unselfish request.
With eisegesis you can say anything you want. The record demonstrates a selfless request. Even God said so.