drm/amd/amdgpu: Enable DCN IP init for Beige Goby

[Why&How]
Adds DCN IP block initialization for Beige Goby

Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>