GPU DDK - kernel<->fw CCB contains SYNC_PRIMITIVE_BLOCK firmware address without holding reference

Software installed and run as a non-privileged user may conduct improper GPU system calls to cause mismanagement of resources creating a write use after free scenario. A shared resource (memory page) managed by a CPU thread of control (driver) and accessed by a GPU thread of control (Firmware) can cause a write UAF when the CPU thread frees the resource before the GPU FW has finished accessing it.