batman-adv: Replace C99 int types with kernel type

(s|u)(8|16|32|64) are the preferred types in the kernel. The use of the
standard C99 types u?int(8|16|32|64)_t are objected by some people and even
checkpatch now warns about using them.

Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Antonio Quartulli <antonio@meshcoding.com>