ixgb: audit use of dev_kfree_skb_any

calls to kfree_skb_any are only required when calling kfree
from interrupt context.

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>