drm/amdgpu: drop redundant sched job cleanup when cs is aborted

Once command submission failed due to userptr invalidation in
amdgpu_cs_submit, legacy code will perform cleanup of scheduler
job. However, it's not needed at all, as former commit has integrated
job cleanup stuff into amdgpu_job_free. Otherwise, because of double
free, a NULL pointer dereference will occur in such scenario.

Bug: drm/amd#2457


Fixes: f7d66fb2 ("drm/amdgpu: cleanup scheduler job initialization v2")
Signed-off-by: Guchun Chen <guchun.chen@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>