drm/amdkfd: Remove unnecessary condition in kfd_topology_add_device()

We re-arranged this code recently so "ret" is always zero at this point.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>