kernel: kmod-macsec module for 4.9

kernel: kmod-macsec module for 4.9

MACsec/IEEE 802.1AE is useful to secure communication to and
from endpoints at Layer 2.

Starting with 4.6, the linux kernel provides a universal
macsec driver for 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

Note:
LEDE can utilize MACsec with a static connectivity association
key (static PSK) with the ip-full package installed.
<http://man7.org/linux/man-pages/man8/ip-macsec.8.html>

Signed-off-by: Christian Lamparter <chunkeey@gmail.com>