drm/amdgpu: use scheduler dependencies for CS

Entirely remove the sync obj in the job.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Luben Tuikov <luben.tuikov@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221014084641.128280-11-christian.koenig@amd.com