drm/amd/powerplay: hint when power profile setting is not supported

Give user some hints when the power profile setting is not supported.

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