batman-adv: Fix misspelled "wont"

checkpatch started to complain about the mispelling of:

  CHECK: 'wont' may be misspelled - perhaps 'won't'?
  #459: FILE: ./net/batman-adv/bat_iv_ogm.c:459:
  +    * - the resulting packet wont be bigger than

Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>