Add l2 fwd kernel module

Add l2 fwd kernel module

This commit adds a simple kernel module for l2 forwarding or termination

This module provides only level 2 forwarding between two ports, it does not
do any NAT or Masquerade.

Arguments are:

net1=ethXXXX # set forwarding port 1
net2=ethXXX  # set forwarding port 2
terminate=1  # terminate the connection and free the skb

Changed to GPL licensing to avoid compilation issues
Added sanity build target
Fix whitespace issues

JIRA: VSPERF-39

Change-Id: I0fa3e0135af06b7cba665a357dccfb9459edb9f6
Signed-off-by: Eugene Snider <eugene.snider@huawei.com>