drm/amdgpu: add pipeline sync for compute job

hardware ring is async processed, the job is executed in parallel.
In some case, this will result vm fault, like jobs with different vmids.

This works around a CPC hw issue which will eventually be fixed in fw.

Signed-off-by: Chunming Zhou <David1.Zhou@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Monk Liu <monk.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>