batman-adv: fix typos in comments

the word millisecond is misspelled in several comments. This patch fixes it.

Signed-off-by: Antonio Quartulli <ordex@autistici.org>
diff --git a/net/batman-adv/vis.h b/net/batman-adv/vis.h
index 84e716e..873282f 100644
--- a/net/batman-adv/vis.h
+++ b/net/batman-adv/vis.h
@@ -20,7 +20,7 @@
 #ifndef _NET_BATMAN_ADV_VIS_H_
 #define _NET_BATMAN_ADV_VIS_H_
 
-/* timeout of vis packets in miliseconds */
+/* timeout of vis packets in milliseconds */
 #define BATADV_VIS_TIMEOUT		200000
 
 int batadv_vis_seq_print_text(struct seq_file *seq, void *offset);