drm/amd/powerplay: disable raven2 force dpm level support (v2)

It's not supported yet.

v2: rebase (Alex)

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