Revert "drm/amdgpu: disable stutter mode for renoir"

This reverts commit 5813f97a

.

Since SBIOS WCD9925N, NMI printing disappeared. Hence enable stutter
mode.

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