igb: correct typo that was setting vfta mask to 1

This patch corrects a typo that was doing a less than comparison instead of
a left shift due to the fact that I didn't get enough <'s in there.

This resolves an issue in which vlans were not functioning correctly.

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>