drm/amd/display: Fix misuse of plane state destroy helper

drm_plane_state is subclassed by dm_plane_state, so atomic driver should
use __drm_atomic_helper_plane_destroy_state() to destroy a state.
drm_atomic_helper_plane_destroy_state() frees drm_plane_state which is
allocated inside dm_plane_state, this is problematic.

Fixes: 95ae03a ("drm/amd/display: Create dm_plane_state.")
Signed-off-by: Xiaojie Yuan <Xiaojie.Yuan@amd.com>
Reviewed-by: Andrey Grodzovsky <Andrey.Grodzovsky@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -1431,7 +1431,8 @@ void dm_drm_plane_destroy_state(struct drm_plane *plane,
 		dc_surface_release(dc_surface);
 	}
 
-	drm_atomic_helper_plane_destroy_state(plane, state);
+	__drm_atomic_helper_plane_destroy_state(state);
+	kfree(dm_plane_state);
 }
 
 static const struct drm_plane_funcs dm_plane_funcs = {