drm/amd/powerplay: add placeholder of smu_initialize_pptable

This patch adds placeholder of smu_initialize_pptable for smu.

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