In a small bowl, whisk together the olive oil, mustard, brown sugar, salt, and pepper. Place the pork chops in a large resealable bag or dish. Pour the marinade over the pork chops and turn to coat. Marinate in the refrigerator for at least 30 minutes, or up to 2 hours. Preheat a grill or grill pan over medium-high heat. Remove the pork chops from the marinade and discard the marinade. Grill the pork chops for 3-4 minutes per side, or until cooked through. Let the pork chops rest for 5 minutes before serving.