drm/amd/display: Only finalize atomic_obj if it was initialized

[Why]
If amdgpu_dm failed to initalize before amdgpu_dm_initialize_drm_device()
completed then freeing atomic_obj will lead to list corruption.

[How]
Check if atomic_obj state is initialized before trying to free.

Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Ivan Lipski <ivan.lipski@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

Author: superm1

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

@@ -5410,7 +5410,8 @@ static int amdgpu_dm_initialize_drm_device(struct amdgpu_device *adev)
 
 static void amdgpu_dm_destroy_drm_device(struct amdgpu_display_manager *dm)
 {
-	drm_atomic_private_obj_fini(&dm->atomic_obj);
+	if (dm->atomic_obj.state)
+		drm_atomic_private_obj_fini(&dm->atomic_obj);
 }
 
 /******************************************************************************