igb: fix i350 anti spoofing config

Fix a problem in i350 where anti spoofing configuration was written into a
wrong register.

Signed-off-by: Lior Levy <lior.levy@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>