igb: Merge VLVF configuration into igb_vfta_set

This change makes it so that we can merge the configuration of the VLVF
registers into the setting of the VFTA register.  By doing this we simplify
the logic and make use of similar functionality that we have already added
for ixgbe making it easier to maintain both drivers.

Signed-off-by: Alexander Duyck <aduyck@mirantis.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>