Staging: batman-adv: fix aggregation timing bug

batman-adv aggregates routing packets to reduce the number of packets in
the air. Every outgoing packet is compared with other packets in the
buffer to determine whether it can be aggregated or not. Packets sent
at a lower interval can be held back longer to maximize the aggregation.
Due to insufficient checking batman-adv held back all packets for a
certain time depending on its own lowest interval rate which slowed
down all other nodes.

Reported-by: Linus Lüssing <linus.luessing@web.de>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>