net: dsa: qca8k: Fix port enable for CPU port

The CPU port does not have a PHY connected to it. So calling
phy_support_asym_pause() results in an Opps. As with other DSA
drivers, add a guard that the port is a user port.

Reported-by: Michal Vokáč <michal.vokac@ysoft.com>
Fixes: 0394a63 ("net: dsa: enable and disable all ports")
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Tested-by: Michal Vokáč <michal.vokac@ysoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/qca8k.c

@@ -936,6 +936,9 @@ qca8k_port_enable(struct dsa_switch *ds, int port,
 {
 	struct qca8k_priv *priv = (struct qca8k_priv *)ds->priv;
 
+	if (!dsa_is_user_port(ds, port))
+		return 0;
+
 	qca8k_port_set_status(priv, port, 1);
 	priv->port_sts[port].enabled = 1;