drm/amd/powerplay: fix set target TDP error on tonga/iceland

ConfigurableTDP do not exist from Fiji.
so only use in previous ASIC.

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>