Revert "drm/amdgpu: Add pci usage to nbio v7.9"

Remove implementation to get pcie usage for nbio v7.9
as pcie usage is handled by fw

This reverts commit 59070fd9.

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