igb: enable RX network flow classification

After apply this series of patches, igb driver will supports advanced RX filter that direct receive packets by flows to different hardware queue. Enables tight control on routing a flow in the platform.

In our product, we use the the RX traffic classification to gurantee the PTP(ethertype is 0x88F7) packets won't be flooded by best effort packet. PTP packets is always be processed by Linux network stack.

step 1.?
? use the ethertype filter to filter most of packet(0x0800) to HW queue; step 2.
? Add a rule to forward the PTP packets to another HW queue

The ethtool commands and options:

-n --show-nfc
?? Retrieves the receive network flow classification configurations

-N --config-nfc
?? Configures the receive network flow classification classification

Change history of this patches:
Version 1:
? Split the patch to 3 patches for review;
? Save the filters and restore them after a reset;
? In ethtool command, use key word "proto" to replace "vlan-etype:
? Fix bugs
Version 2:
? Rebase the patches on the the latest dev-queue; Version 3:
? Report a meaningful error code for misoperation; Version 4:
? Rebase the patches on latest dev-queue;
? Update the patch description and code comments;? Version 5:
? Rebase the patches on latest dev-queue;
? Update the patch description;