use ppfeaturemask to enable/disable stutter mode.
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Reviewed-by: NHuang Rui <ray.huang@amd.com>
Signed-off-by: NRex Zhu <Rex.Zhu@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>