drm/amd/display: Disable idle optimization when PSR is enabled

[Why]
Idle optimization and PSR conflict each other. If both enabled
at the same time, display flickering will be observed.

[How]
Disable idle optimization when PSR is enabled.

Signed-off-by: Zhan Liu <zhan.liu@amd.com>
Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>