drm/amd/display: Only keep cursor p-state force for FPO

[Description]
If transitioning from an FPO config -> FPO config, we want
to keep cursor P-State force disallowed. Any other transition
from FPO config -> non FPO config should unforce the cursor
P-State disallow

Reviewed-by: Wesley Chalmers <Wesley.Chalmers@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Alvin Lee <Alvin.Lee2@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>