It is required by firmware to wait up to 2 seconds for pending commands
before sending the destroy hardware context command. After 2 seconds
wait, if there are still pending commands, driver needs to cancel them.
So the context destroy steps need to be:
1. Stop drm scheduler. (drm_sched_entity_destroy)
2. Wait up to 2 seconds for pending commands.
3. Destroy hardware context and cancel the rest pending requests.
4. Wait all jobs associated with the hwctx are freed.
5. Free job resources.
Signed-off-by: Lizhi Hou <lizhi.hou@xxxxxxx>