batman-adv: Use chain pointer when purging fragments

The chain pointer was already created in batadv_frag_purge_orig to make the
checks more readable. Just use the chain pointer everywhere instead of
having the same dereference + array access in the most lines of this
function.
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Acked-by: Martin Hundebøll <martin@hundeboll.net>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Antonio Quartulli <antonio@meshcoding.com>

net/batman-adv/fragmentation.c

@@ -71,14 +71,14 @@ void batadv_frag_purge_orig(struct batadv_orig_node *orig_node,
 
 	for (i = 0; i < BATADV_FRAG_BUFFER_COUNT; i++) {
 		chain = &orig_node->fragments[i];
-		spin_lock_bh(&orig_node->fragments[i].lock);
+		spin_lock_bh(&chain->lock);
 
 		if (!check_cb || check_cb(chain)) {
-			batadv_frag_clear_chain(&orig_node->fragments[i].head);
-			orig_node->fragments[i].size = 0;
+			batadv_frag_clear_chain(&chain->head);
+			chain->size = 0;
 		}
 
-		spin_unlock_bh(&orig_node->fragments[i].lock);
+		spin_unlock_bh(&chain->lock);
 	}
 }