dsa: correctly determine the number of switches in a system

The number of connected switches was sourced from the number of
children to the DSA node, change it to the number of available
children, skipping any disabled switches.

Fixes: 5e95329b ("dsa: add device tree bindings to register DSA switches")
Signed-off-by: Tobias Waldekranz <tobias@waldekranz.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/dsa/dsa.c

@@ -603,7 +603,7 @@ static int dsa_of_probe(struct platform_device *pdev)
 
 	pdev->dev.platform_data = pd;
 	pd->netdev = &ethernet_dev->dev;
-	pd->nr_chips = of_get_child_count(np);
+	pd->nr_chips = of_get_available_child_count(np);
 	if (pd->nr_chips > DSA_MAX_SWITCHES)
 		pd->nr_chips = DSA_MAX_SWITCHES;