It is possible to drive with a broken shock mount, but it is not recommended to do so. A broken shock mount on one side of the motorcycle means that all the rear suspension is now transferred to one shock on the back of the bike. This can cause issues with controlling the motorcycle and will eventually lead to breaking the other shock mount, which can lead to a crash. You also need to make sure that you have enough clearance for the rear wheel to turn without rubbing on the fender or any other part of the motorcycle.