It's used by more than just DCN2.0.  Fixes missing symbol when
amdgpu is built without DCN support.
Reviewed-by: Zhan Liu <zhan.liu@amd.com>
Tested-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>