drm/amdgpu/acpi: fix typo in ATCS handling

Path should be NULL when we already have the handle
to the object.

Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Tested-by: Sathishkumar S <sathishkumar.sundararaju@amd.com>
Reviewed-by: Sathishkumar S <sathishkumar.sundararaju@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>