net: Add generic network interface header

This will be used by the new network stack to relate a device to actual
network context, and used in the different layers (mac, ip ...).

Change-Id: I30c08fa975314544c36b71636fd9653d562891b3
Signed-off-by: Tomasz Bursztyka <tomasz.bursztyka@linux.intel.com>
5 files changed