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

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().

Signed-off-by: Ketil Johnsen <ketil.johnsen@arm.com>
Fixes: de85488138247 ("drm/panthor: Add the scheduler logical block")
Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
Link: https://patch.msgid.link/20251027140217.121274-1-ketil.johnsen@arm.com
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>