igb: Add MAC address support for ethtool nftuple filters

This adds the capability of configuring the queue steering of arriving
packets based on their source and destination MAC addresses.

Source address steering (i.e. driving traffic to a specific queue),
for the i210, does not work, but filtering does (i.e. accepting
traffic based on the source address). So, trying to add a filter
specifying only a source address will be an error.

In practical terms this adds support for the following use cases,
characterized by these examples:

$ ethtool -N eth0 flow-type ether dst aa:aa:aa:aa:aa:aa action 0
(this will direct packets with destination address "aa:aa:aa:aa:aa:aa"
to the RX queue 0)

$ ethtool -N eth0 flow-type ether src 44:44:44:44:44:44 \
  	     	  	    	  proto 0x22f0 action 3
(this will direct packets with source address "44:44:44:44:44:44" and
ethertype 0x22f0 to the RX queue 3)

Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>