drm/panthor: Fix UAF race between device unplug and FW event processing

In the Linux kernel, the following vulnerability has been resolved: drm/panthor: Fix UAF race between device unplug and FW event processing The function panthor_fw_unplug() will free the FW memory sections. The problem is that there could still be pending FW events which are yet not handled at this point. process_fw_events_work() can in this case try to access said freed memory. Simply call disable_work_sync() to both drain and prevent future invocation of process_fw_events_work().