6lowpan: add missing spin_lock_init()

Add missing spin_lock_init() for frames list lock.

Signed-off-by: Alexander Smirnov <alex.bluesman.smirnov@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ieee802154/6lowpan.c b/net/ieee802154/6lowpan.c
index b3021f7..840821b 100644
--- a/net/ieee802154/6lowpan.c
+++ b/net/ieee802154/6lowpan.c
@@ -1168,6 +1168,8 @@
 	list_add_tail(&entry->list, &lowpan_devices);
 	mutex_unlock(&lowpan_dev_info(dev)->dev_list_mtx);
 
+	spin_lock_init(&flist_lock);
+
 	register_netdevice(dev);
 
 	return 0;