drm/sched: Cleanup gpu_scheduler trace events

A fence uniquely identify a job, so this commits updates the places
where a kernel pointer was used as an identifier by:

   "fence=%llu:%llu"

Signed-off-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Signed-off-by: Philipp Stanner <phasta@kernel.org>
Link: https://lore.kernel.org/r/20250526125505.2360-5-pierre-eric.pelloux-prayer@amd.com