batman-adv: correct several typ0s in the comments

Several typos have been corrected and some sentences have been rephrased

Signed-off-by: Antonio Quartulli <ordex@autistici.org>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
diff --git a/net/batman-adv/vis.c b/net/batman-adv/vis.c
index 8b75cc5..fb9b19f 100644
--- a/net/batman-adv/vis.c
+++ b/net/batman-adv/vis.c
@@ -131,7 +131,7 @@
 			return;
 	}
 
-	/* its a new address, add it to the list */
+	/* it's a new address, add it to the list */
 	entry = kmalloc(sizeof(*entry), GFP_ATOMIC);
 	if (!entry)
 		return;