drm/amd/sched: fix job tear down order v2

Move the trace before we signal the scheduler fence and drop the
scheduler fence reference directly before we free the job.

v2: keep extra s_fence reference

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Liu, Monk <Monk.Liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>