drm/amd/powerplay: add sys interface for pcie for smu

Add sys interface for set/get PCIE info for SMU.
The related operate will do nothing as vega20 do not support it now.

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>