OK Since posting this I just saw the answer above and if the schematics are indeed available that must be the answer. There are so many small square surface mount ICs. But rather than just delete my comment this is what I wrote without that info (probably wrong):
It's very hard to tell from the photo. What we need to know is how many connections does it have in the land pattern. Some web searching for C7 makes me think it might be a SN74LVC1G17 which has a square package. It has five connections. Four on the corners plus the central thermal pad in one version. It looks more like an integrated circuit to me than a diode or something passive.
The amount of gunk around it makes it hard to tell what the copper pad pattern looks like.
I would check out the texas instruments SN74LVC1G17 Single Schmitt-Trigger Buffer. It makes sense electrically that it would be near a connector because typically a buffer like that is to receive an input from off board which might be noisy.
Annoyingly they seem to have a number of versions of the same chip which are all about 1mm square, with different connection styles, e.g. ball grid, or whatever. I would carefully look at the datasheet and maybe try to expose the copper land pattern of the board and see which it might be.
Update: Yeah it could be a voltage regulator absolutely - with the same package. Probably you'd have to buy one from Mouser/Digikey to see if it looks the same.