drm/amdgpu/powerplay: implement pem_task for display_configuration_change

Add support for display configuration changes to the event manager.

Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Reviewed-by: Jammy Zhou <Jammy.Zhou@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>