Just wait for last fence instead of waiting for the sequence manually.

v2: don't use amdgpu_sched_jobs for the mask
Signed-off-by: Christian König <christian.koenig@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Chunming Zhou <david1.zhou@amd.com>