ixgbe: fix ntuple support

commit f62bbb5e
ixgbe: Update ixgbe to use new vlan accleration.

removed ETH_FLAG_NTUPLE from the supported flags.

This patch puts it back on to allow for setting ntuple via ethtool.

CC: Jesse Gross <jesse@nicira.com>
Signed-off-by: Emil Tantilov <emil.s.tantilov@intel.com>
Tested-by: Stephen Ko <stephen.s.ko@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>