igb: remove netif running call from igb_poll

The netif_running check in igb poll is a hold over from the use of fake
netdevs to use multiple queues with NAPI prior to 2.6.24.  It is no longer
necessary to have the call there and it currently can cause errors if
work_done == budget.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Acked-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>