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: Alexander Duyck <alexander.h.duyck@intel.com>
Acked-by:  Mallikarjuna R Chilakala <mallikarjuna.chilakala@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ixgbe/ixgbe_main.c b/drivers/net/ixgbe/ixgbe_main.c
index 2ad754c..3859767 100644
--- a/drivers/net/ixgbe/ixgbe_main.c
+++ b/drivers/net/ixgbe/ixgbe_main.c
@@ -5576,6 +5576,10 @@
 	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;