drm/amdgpu: add psp support for navy_flounder

Currently skip ASD FW loading and ih reroute per
sienna_cichlid.

Signed-off-by: Jiansong Chen <Jiansong.Chen@amd.com>
Reviewed-by: Tao Zhou <tao.zhou1@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>