drm/amd/powerplay: add two interfaces to set_active_display_count and store_cc6_data

This patch adds two interfaces to set_active_display_count and store_cc6_data,
they won't be used for smu11, and just be the placeholders for future asic on
display to smu interface.

Signed-off-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Evan Quan <evan.quan@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>