drm/amd/display: Release cached atomic state in S3.

Fixes memory leak.
Signed-off-by: Andrey Grodzovsky <Andrey.Grodzovsky@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -508,6 +508,7 @@ static int dm_suspend(void *handle)
 
 	amdgpu_dm_irq_suspend(adev);
 
+	WARN_ON(adev->dm.cached_state);
 	adev->dm.cached_state = drm_atomic_helper_suspend(adev->ddev);
 
 	dc_set_power_state(
@@ -607,6 +608,9 @@ int amdgpu_dm_display_resume(struct amdgpu_device *adev )
 
 	ret = drm_atomic_helper_resume(ddev, adev->dm.cached_state);
 
+	drm_atomic_state_put(adev->dm.cached_state);
+	adev->dm.cached_state = NULL;
+
 	amdgpu_dm_irq_resume_late(adev);
 
 	return ret;