igc: Report VLAN EtherType matching back to user

Currently the driver allows to configure matching by VLAN EtherType.
However, the retrieval function does not report it back to the user. Add
it.

Before:
|root@host:~# ethtool -N enp3s0 flow-type ether vlan-etype 0x8100 action 0
|Added rule with ID 63
|root@host:~# ethtool --show-ntuple enp3s0
|4 RX rings available
|Total 1 rules
|
|Filter: 63
|        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
|        Action: Direct to queue 0

After:
|root@host:~# ethtool -N enp3s0 flow-type ether vlan-etype 0x8100 action 0
|Added rule with ID 63
|root@host:~# ethtool --show-ntuple enp3s0
|4 RX rings available
|Total 1 rules
|
|Filter: 63
|        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: 0x8100 mask: 0x0
|        VLAN: 0x0 mask: 0xffff
|        User-defined: 0x0 mask: 0xffffffffffffffff
|        Action: Direct to queue 0

Fixes: 2b477d05

 ("igc: Integrate flex filter into ethtool ops")
Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>
Acked-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Tested-by: Naama Meir <naamax.meir@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>