drm/amdgpu: Enable S/G for Yellow Carp

commit c5d3c9a0 upstream.

Missing code for Yellow Carp to enable scatter gather - follows how
DCN21 support was added.

Tested that 8k framebuffer allocation and display can now succeed after
applying the patch.

v2: Add hookup in DM

Reviewed-by: Aaron Liu <aaron.liu@amd.com>
Acked-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>