drm/amd/display: Fix dcn401_optimize_bandwidth

drm/amd/display: Fix dcn401_optimize_bandwidth

[Why&How]
We should check for != zstate disallow and programming extend blank from a
different struct.

Reviewed-by: Leo Chen <leo.chen@amd.com>
Reviewed-by: Dmytro Laktyushkin <dmytro.laktyushkin@amd.com>
Signed-off-by: Charlene Liu <Charlene.Liu@amd.com>
Signed-off-by: Ivan Lipski <ivan.lipski@amd.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>