ixgbe: fix vlan filtering

VLAN filtering is broken, due to reading the incorrect register for
the VLAN filtering settings.  Fixed by reading/writing the correct
register.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
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>