I don't think there is a policy, is there? I know that the guidance says that edits to other people's posts should be "substantial", but it also says that the OP "may always edit their own post".
Besides, isn't there an SE "Community" process that also bumps posts?
I assume that 'bump' edits are intended to gain reputation &/or badges. If so, I suppose that down-voting posts may be an effective deterrent?
Of course, I may be entirely wrong about the motivation. To be fair, I'm not sure that I really get the whole reputation/badges system as motivation, so perhaps I should take a moment to explain how I see it.
Yes, it makes perfect sense to me that there is a system of "reputation" that gradually opens features of the site as users gain more experience (and hence "reputation" points). But once a user has unlocked all the site privileges the system has the potential to become counter-productive.
Besides, a "poor" answer is a poor answer, whether it's posted by a user with a reputation of 100 or a user with a reputation of 100K.
As for badges, when I first heard that SE awarded badges for participation it reminded me a little of the days when we were given gold stars at primary school. It also brought to mind a scene from Mel Brook's 1974 classic movie spoof "Blazing Saddles"! (Google is your friend if you're not familiar with it)
[Having said all that, given how much I've had to fight against people telling me to specialise over the years, the idea of a "Generalist" badge does have a sneaking appeal, even to an old cynic like me! ;-)]
Having said all that, I'm not sure we need a more specific policy to deal with 'bump' edits. When the OP edits their post, there is an opportunity for people to retract or change their votes. If people really feel that 'bump' edits are a problem that would seem to be an effective way of dealing with it.