batman-adv: Always send iface index+name in genlmsg

batman-adv: Always send iface index+name in genlmsg

The batman-adv netlink messages often contain the interface index and
interface name in the same message. This makes it easy for the receiver to
operate on the incoming data when it either needs to print something or
needs to operate on the interface index.

But one of the attributes was missing for:

* neighbor table dumps
* originator table dumps
* gateway list dumps
* query of hardif information
* query of vid information

The userspace therefore had to implement special workarounds using
SIOCGIFNAME or SIOCGIFINDEX depending on what was actually provided.
Providing both information simplifies the userspace code massively without
adding a lot of extra overhead in the kernel portion.

Signed-off-by: Sven Eckelmann <sven@narfation.org>