ixgbe: Do not attempt to perform interrupts in netpoll when down

This patch resolves issues seen when running netconsole and rebooting via
reboot -f.  The issue was due to the fact that we were attempting to
perform interrupt actions when the q_vectors and rings had already been
freed via the ixgbe_shutdown routines.
Signed-off-by: NAlexander Duyck <alexander.h.duyck@intel.com>
Acked-by: NMallikarjuna R Chilakala <mallikarjuna.chilakala@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ixgbe/ixgbe_main.c

@@ -5576,6 +5576,10 @@ static void ixgbe_netpoll(struct net_device *netdev)
 	struct ixgbe_adapter *adapter = netdev_priv(netdev);
 	int i;
 
+	/* if interface is down do nothing */
+	if (test_bit(__IXGBE_DOWN, &adapter->state))
+		return;
+
 	adapter->flags |= IXGBE_FLAG_IN_NETPOLL;
 	if (adapter->flags & IXGBE_FLAG_MSIX_ENABLED) {
 		int num_q_vectors = adapter->num_msix_vectors - NON_Q_VECTORS;