net: bt: Fix failing to resolve link-local address This make sure the link-local address of the destination is added to the nbr cache as that is accessed when calling net_ipv6_prepare_for_send, this is needed when following RFC 7668 since link-local addresses are never registered using nbr discovery. Change-Id: I2bc578d33d1061726d0cbf46e4464df74d79e992 Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>