drm/amdgpu: remove v_seq handling from the scheduler v2

Simply not used any more. Only keep 32bit atomic for fence sequence numbering.

v2: trivial rebase

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com> (v1)
Reviewed-by: Jammy Zhou <Jammy.Zhou@amd.com> (v1)
Reviewed-by: Chunming Zhou <david1.zhou@amd.com> (v1)