net: dsa: retain a per-port device_node pointer

We will later use the per-port device_node pointer to fetch a bunch of
port-specific properties.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c
index a28ef43..6a5bae6 100644
--- a/net/dsa/dsa.c
+++ b/net/dsa/dsa.c
@@ -432,6 +432,8 @@
 			if (!port_name)
 				continue;
 
+			cd->port_dn[port_index] = port;
+
 			cd->port_names[port_index] = kstrdup(port_name,
 					GFP_KERNEL);
 			if (!cd->port_names[port_index]) {