batman-adv: remove bonding and interface alternating

Remove bonding and interface alternating code - it will be replaced
by a new, network-wide multi interface optimization which enables
both bonding and interface alternating in a better way.

Keep the sysfs and find router function though, this will be needed
later.

Signed-off-by: Simon Wunderlich <simon@open-mesh.com>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Antonio Quartulli <antonio@meshcoding.com>