ixgbe: Add support for toggling VLAN filtering flag via ethtool

This change makes it so that we can use the ethtool rx-vlan-filter flag to
toggle Rx VLAN filtering on and off.  This is basically just an extension
of the existing VLAN promisc work in that it just adds support for the
additional ethtool flag.

Signed-off-by: Alexander Duyck <aduyck@mirantis.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>