drm/amdgpu: Add stutter mode ctrl in module parameter

drm/amdgpu: Add stutter mode ctrl in module parameter

Enable stutter mode can save power in low DRAM use cases
including but not limited to productivity application use,
web browsing, and video playback.

Currently this feature is disabled by default.

Make bit 17 in module parameter amdgpu_pp_feature_mask
as stutter mode mask, so user can enable/disable this feature easily.

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>