net: dsa: cleanup resources upon module removal

Make sure that we unassign the master_netdev dsa_ptr to make the packet
processing go through the regular Ethernet receive path.
Suggested-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/dsa/dsa.c

@@ -985,6 +985,14 @@ static int dsa_suspend(struct device *d)
 	struct dsa_switch_tree *dst = platform_get_drvdata(pdev);
 	int i, ret = 0;
 
+	dst->master_netdev->dsa_ptr = NULL;
+
+	/* If we used a tagging format that doesn't have an ethertype
+	 * field, make sure that all packets from this point get sent
+	 * without the tag and go through the regular receive path.
+	 */
+	wmb();
+
 	for (i = 0; i < dst->pd->nr_chips; i++) {
 		struct dsa_switch *ds = dst->ds[i];