batman-adv: Fix spelling error in term buffer

checkpatch warns about a typo in the word bufFer which was introduced in
commit 2191c1bcbc64 ("batman-adv: kernel doc for types.h").
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>

net/batman-adv/types.h

@@ -1086,7 +1086,7 @@ struct batadv_priv_bla {
  * struct batadv_priv_debug_log - debug logging data
  */
 struct batadv_priv_debug_log {
-	/** @log_buff: buffer holding the logs (ring bufer) */
+	/** @log_buff: buffer holding the logs (ring buffer) */
 	char log_buff[BATADV_LOG_BUF_LEN];
 
 	/** @log_start: index of next character to read */