net: if: Join/leave pre-defined IPv6 multicast groups

When we setup the network interface, add predefined IPv6 multicast
groups into the network interface. When interface is taken down,
then leave all the multicast groups that joined.
See RFC 4291 ch 2.8 for details.

Change-Id: If17d3e8c75157a02aa93c92e2fb499619c1484cf
Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>