drm/dp_mst: Zero assigned PBN when releasing VCPI slots

Zero Port's PBN together with VCPI slots when releasing
allocated VCPI slots. That way when disabling the connector
it will not cause issues in drm_dp_mst_atomic_check verifying
branch bw limit.

Signed-off-by: Mikita Lipski <[email protected]>
Signed-off-by: Lyude Paul <[email protected]>
Fixes: cd82d82 ("drm/dp_mst: Add branch bandwidth validation to MST atomic check")
Cc: <[email protected]> # v5.6+
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

Author: Mikita Lipski

drivers/gpu/drm/drm_dp_mst_topology.c

@@ -4295,6 +4295,7 @@ int drm_dp_atomic_release_vcpi_slots(struct drm_atomic_state *state,
 	if (pos->vcpi) {
 		drm_dp_mst_put_port_malloc(port);
 		pos->vcpi = 0;
+		pos->pbn = 0;
 	}
 
 	return 0;