drm/amdgpu: handle multi level PD size calculation (v2)

Allows us to get the size for all levels as well.

v2: agd: fix warning

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Junwei Zhang <Jerry.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>