drm/sched/tests: Implement cancel_job() callback
The GPU Scheduler now supports a new callback, cancel_job(), which lets
the scheduler cancel all jobs which might not yet be freed when
drm_sched_fini() runs. Using this callback allows for significantly
simplifying the mock scheduler teardown code.
Implement the cancel_job() callback and adjust the code where necessary.
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Signed-off-by: Philipp Stanner <phasta@kernel.org>
Link: https://lore.kernel.org/r/20250710125412.128476-5-phasta@kernel.org