drm/amdgpu: remove gpu_info fw support for sienna_cichlid etc.

Remove gpu_info fw support for sienna_cichlid etc., since the
information can be retrieved from discovery binary.

Signed-off-by: Jiansong Chen <Jiansong.Chen@amd.com>
Reviewed-by: Likun Gao <Likun.Gao@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>