drm/amdgpu: Initialize VF partition mode

For SOCs with GFX v9.4.3, a VF may have multiple compute partitions.
Fetch the partition information during init and initialize partition
nodes. There is no support to switch partition mode in VF mode, hence
disable the same.

Signed-off-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>