drm/amd/powerplay: correct fine grained dpm force level setting

For fine grained dpm, there is only two levels supported. However
to reflect correctly the current clock frequency, there is an
intermediate level faked. Thus on forcing level setting, we
need to treat level 2 correctly as level 1.

Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Kevin Wang <kevin1.wang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>