net: dsa: Do not suspend/resume closed slave_dev

BugLink: https://bugs.launchpad.net/bugs/1791953

[ Upstream commit a94c689e ]

If a DSA slave network device was previously disabled, there is no need
to suspend or resume it.

Fixes: 24462549 ("net: dsa: allow switch drivers to implement suspend/resume hooks")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

net/dsa/slave.c

@@ -1099,6 +1099,9 @@ int dsa_slave_suspend(struct net_device *slave_dev)
 {
 	struct dsa_slave_priv *p = netdev_priv(slave_dev);
 
+	if (!netif_running(slave_dev))
+		return 0;
+
 	netif_device_detach(slave_dev);
 
 	if (p->phy) {
@@ -1116,6 +1119,9 @@ int dsa_slave_resume(struct net_device *slave_dev)
 {
 	struct dsa_slave_priv *p = netdev_priv(slave_dev);
 
+	if (!netif_running(slave_dev))
+		return 0;
+
 	netif_device_attach(slave_dev);
 
 	if (p->phy) {