net: dsa: store CPU switch structure in the tree

Store a dsa_switch pointer to the CPU switch in the tree instead of only
its index. This avoids the need to initialize it to -1.

Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-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 fd53248..b220609 100644
--- a/net/dsa/dsa.c
+++ b/net/dsa/dsa.c
@@ -225,12 +225,12 @@
 			continue;
 
 		if (!strcmp(name, "cpu")) {
-			if (dst->cpu_switch != -1) {
+			if (!dst->cpu_switch) {
 				netdev_err(dst->master_netdev,
 					   "multiple cpu ports?!\n");
 				return -EINVAL;
 			}
-			dst->cpu_switch = index;
+			dst->cpu_switch = ds;
 			dst->cpu_port = i;
 			ds->cpu_port_mask |= 1 << i;
 		} else if (!strcmp(name, "dsa")) {
@@ -254,7 +254,7 @@
 	 * tagging protocol to the preferred tagging format of this
 	 * switch.
 	 */
-	if (dst->cpu_switch == index) {
+	if (dst->cpu_switch == ds) {
 		enum dsa_tag_protocol tag_protocol;
 
 		tag_protocol = ops->get_tag_protocol(ds);
@@ -757,7 +757,6 @@
 
 	dst->pd = pd;
 	dst->master_netdev = dev;
-	dst->cpu_switch = -1;
 	dst->cpu_port = -1;
 
 	for (i = 0; i < pd->nr_chips; i++) {