drm/amdgpu: disable stutter mode for renoir

With stutter mode enabled, NMI prints frequently.
Disable stutter for the moment because NMI warning storm, and will
enable it back till the issue is addressed

Signed-off-by: Aaron Liu <aaron.liu@amd.com>
Acked-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>