macsec: introduce IEEE 802.1AE driver

This is an implementation of MACsec/IEEE 802.1AE.  This driver
provides authentication and encryption of traffic in a LAN, typically
with GCM-AES-128, and optional replay protection.

http://standards.ieee.org/getieee802/download/802.1AE-2006.pdf



Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Reviewed-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>