drm/amd/powerplay: correct SW SMU valid mapping check

Current implementation is not actually able to detect
invalid message/table/workload mapping.

Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Feifei Xu <Feifei.Xu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>