Treat it a bit like the first day at nursery and don't draw out the goodbye (but to stop you crying not him)
You cry all you like when you are back in the car!
If he is in halls, it may be super busy there as everyone arrives at the same time- lonf queues for the car park etc.
Pack his duvet, pillow and bedsheets into one bag, make the bed up for him and prepare to leave fairly quickly (again, because of the need to move everyone in, you may be encouraged/required not to linger by only allowing cars to park for fixed time. So be aware that could be the case.
He may not unpack his clothes for weeks but at least you will know he is in a clean bed with sheets on it after the first night in the hall bar.
If he is in self catered halls, arrive with a few bits of food (milk, cereal, bread, pasta, sauce) but don't get much fresh in as he may be our and about a lot in the first few weeks and fresh stuff will go to waste.
You may find the car park has more than a few crying parents but almost everyone holds it together until they have left.
And he will be back very soon. Terms are not that long and often they can't stay in halls over the holidays so you will have him back for nearly a month over xmas