ixgbe: Fix netpoll to be properly multiqueue aware

Our ndo_poll_controller callback is broken for anything but non-multiqueue
setups.  This fixes that issue.

Signed-off-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>