drm/amdgpu: add vega12 to dc support check

DC is used for modesetting on vega12.

Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Feifei Xu <Feifei.Xu@amd.com>
1 file changed