Current implementation of net_ipv6_send_rs() uses
net_ipv6_addr_create_ll_allnodes_mcast() for creating RS packet.
As result we send RS packet to all-nodes destination [FF02::1],
but RFC4291 requires all-routers destination [FF02::2] for RS packets.
Signed-off-by: Eug Krashtan <eug.krashtan@gmail.com>
