batman-adv: Keep includes ordered by filename

It is easier to detect if a include is already there for a used
functionality when the includes are ordered. Using an alphabetic order
together with the grouping in commit 1e2c2a4fe4a5 ("batman-adv: Add
required includes to all files") makes includes better manageable.

Signed-off-by: Sven Eckelmann <[email protected]>
Signed-off-by: Marek Lindner <[email protected]>
Signed-off-by: Simon Wunderlich <[email protected]>
7 files changed