ixgbe: add Tx anti spoofing support

This patch enables the ethertype Anti-Spoofing feature for affected
devices. It is configured such that LLDP packets sent by a VF will
be dropped.

Signed-off-by: Don Skidmore <donald.c.skidmore@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>