drm/amdgpu: Add PSP interface for NPS switch

Implement PSP ring command interface for memory partitioning on the fly
on the supported asics.

Signed-off-by: Rajneesh Bhardwaj <rajneesh.bhardwaj@amd.com>
Reviewed-by: Feifei Xu <Feifei.Xu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>