batman-adv: netlink: add originator and neighbor table queries

Add BATADV_CMD_GET_ORIGINATORS and BATADV_CMD_GET_NEIGHBORS commands,
using handlers bat_orig_dump and bat_neigh_dump in batadv_algo_ops. Will
always return -EOPNOTSUPP for now, as no implementations exist yet.

Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
[sven@narfation.org: Rewrite based on new algo_ops structures]
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>