drm/amdgpu: enable IH ring 1&2 for Vega20 as well

That doesn't seem to have any negative effects.

Signed-off-by: Christian König <christian.koenig@amd.com>
Acked-by: Chunming Zhou <david1.zhou@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>