hw: Add static helper for constructing IPv6 mcast MAC addresses
hw: Add static helper for constructing IPv6 mcast MAC addresses

mnordsletten/IncludeOS,hioa-cs/IncludeOS,hioa-cs/IncludeOS,AndreasAakesson/IncludeOS,alfred-bratterud/IncludeOS,AndreasAakesson/IncludeOS,hioa-cs/IncludeOS,AndreasAakesson/IncludeOS,AnnikaH/IncludeOS,mnordsletten/IncludeOS,alfred-bratterud/IncludeOS,AnnikaH/IncludeOS,hioa-cs/IncludeOS,alfred-bratterud/IncludeOS,AndreasAakesson/IncludeOS,AnnikaH/IncludeOS,AndreasAakesson/IncludeOS,AnnikaH/IncludeOS,AnnikaH/IncludeOS,alfred-bratterud/IncludeOS,AndreasAakesson/IncludeOS,hioa-cs/IncludeOS,mnordsletten/IncludeOS,mnordsletten/IncludeOS,mnordsletten/IncludeOS,alfred-bratterud/IncludeOS,mnordsletten/IncludeOS