drm/amdgpu: support nbio_7_2_1 for yellow carp

This patch adds nbio_7_2_1 support yellow carp.

Signed-off-by: Aaron Liu <aaron.liu@amd.com>
Reviewed-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>