net: Add a neighbor cache needed in IPv6

This is the framework that neighbor discovery uses. The ND
is coming in later commits.

Change-Id: Iaaa67c80c0b6b8a3adb9217413b906e0a22d3920
Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>
5 files changed