drm/amdgpu: remove gpu info firmware of green sardine

The ip discovery is supported on green sardine, it doesn't need gpu info
firmware anymore.

Signed-off-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Prike Liang <Prike.Liang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>