igb: support RX flow classification by VLAN priority

This patch is meant to allow for RX network flow classification to insert
and remove VLAN priority filter by ethtool

Example:
Add an VLAN priority filter:
$ ethtool -N eth0 flow-type ether vlan 0x6000 vlan-mask 0x1FFF action 2 loc 1

Show all filters:
$ ethtool -n eth0
4 RX rings available
Total 1 rules

Filter: 1
	Flow Type: Raw Ethernet
	Src MAC addr: 00:00:00:00:00:00 mask: FF:FF:FF:FF:FF:FF
	Dest MAC addr: 00:00:00:00:00:00 mask: FF:FF:FF:FF:FF:FF
	Ethertype: 0x0 mask: 0xFFFF
	VLAN EtherType: 0x0 mask: 0xffff
	VLAN: 0x6000 mask: 0x1fff
	User-defined: 0x0 mask: 0xffffffffffffffff
	Action: Direct to queue 2

Delete the filter by location:
$ ethtool -N delete 1

Signed-off-by: Ruhao Gao <ruhao.gao@ni.com>
Signed-off-by: Gangfeng Huang <gangfeng.huang@ni.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>