Staging: batman-adv: Refactor routing.c

Break up a lot of the big functions up into many smaller ones. This
helps with readability and there is now a lot less code squashed
against the right hand margin.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Marek Lindner <lindner_marek@yahoo.de>
Acked-by: Simon Wunderlich <simon.wunderlich@s2003.tu-chemnitz.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>