net: nbuf: Set the link address type in nbuf

When we know the network interface where the packet is about
to be sent, then set the link address type too.

The link address type is used when working with IPv6 link
local and auto configured addresses.

Change-Id: If086c3c413c025809cffa64311f973bc7bdac7db
Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>