batman-adv: Fix kernel-doc for timer functions

The commit e99e88a9 ("treewide: setup_timer() -> timer_setup()")
changed the argument name and type of the timer function but didn't adjust
the kernel-doc of these functions.

Signed-off-by: Sven Eckelmann <sven@narfation.org>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>