drm/amd/powerplay: add function to update overdrive settings

Add function of smu_update_specified_od8_value to modify specified
overdrive value.
Add fucntion of smu_update_od8_settings to update overdrive table.

Signed-off-by: Likun Gao <Likun.Gao@amd.com>
Reviewed-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Kevin Wang <kevin1.wang@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>