batman-adv: Fix broadcast/ogm queue limit on a removed interface

When removing a single interface while a broadcast or ogm packet is
still pending then we will free the forward packet without releasing the
queue slots again.

This patch is supposed to fix this issue.

Fixes: 6d5808d4 ("batman-adv: Add missing hardif_free_ref in forw_packet_free")
Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
[sven@narfation.org: fix conflicts with current version]
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Antonio Quartulli <a@unstable.cc>