drm/amdgpu: use scheduler dependencies for VM updates

Instead of putting that into the job sync object.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Luben Tuikov <luben.tuikov@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221014084641.128280-9-christian.koenig@amd.com