net: aquantia: oops when shutdown on already stopped device

In case netdev is closed at the moment of pci shutdown, aq_nic_stop
gets called second time. napi_disable in that case hangs indefinitely.
In other case, if device was never opened at all, we get oops because
of null pointer access.

We should invoke aq_nic_stop conditionally, only if device is running
at the moment of shutdown.

Reported-by: David Arcari <darcari@redhat.com>
Fixes: 90869ddfef ("net: aquantia: Implement pci shutdown callback")
Signed-off-by: Igor Russkikh <igor.russkikh@aquantia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/aquantia/atlantic/aq_nic.c

@@ -951,9 +951,11 @@ void aq_nic_shutdown(struct aq_nic_s *self)
 
 	netif_device_detach(self->ndev);
 
-	err = aq_nic_stop(self);
-	if (err < 0)
-		goto err_exit;
+	if (netif_running(self->ndev)) {
+		err = aq_nic_stop(self);
+		if (err < 0)
+			goto err_exit;
+	}
 	aq_nic_deinit(self);
 
 err_exit: